Here,

3x2 - 5xy - 2y2 - x + 2y = 0

or, 3x2 - 6xy + xy - 2y2 - x + 2y = 0

or, 3x(x - 2y) + y(x - 2y) - 1(x - 2y) = 0

or, (x - 2y) (3x + y - 1) = 0

Either: x - 2y = 0

Or: 3x + y - 1 = 0

∴ The required equations are: x - 2y = 0 and 3x + y - 1 = 0Ans

Here,

x2 - 3xy + 2y2 = 0

or, x2 - 2xy - xy + 2y2 = 0

or, x(x - 2y) - y(x - 2y) = 0

or, (x - 2y) (x - y) = 0

Either: x - 2y = 0

Or: x - y = 0

∴ The required seperate equations are:x - 2y = 0 andx - y = 0 Ans

Here,

The given equation is:6x2 + 11xy - 6y2 = 0..................(1)

The homogeneous equation of second is: ax2 + 2hxy + by2 = 0.................(2)

Comparing (1) and (2)

a = 6

2h = 11 i.e. h = $$\frac {11}2$$

b = -6

Now.

a + b = 0

or, 6 - 6 = 0

∴ 0 = 0

Hence, a + b = 0 is satisfied by the given equation so the equation6x2 + 11xy - 6y2 = 0 are perpendicular to each other. Proved

Here,

Given equation is:x2 - 4xy + 4y2 = 0......................(1)

The homogenous equation of second degree is:

ax2+ 2hxy + by2 = 0...........................(2)

Comparing (1) and (2)

a = 1

2h = -4 i.e. h = $$\frac {-4}2$$ = -2

b = 4

Now,

h2 = ab

or, (-2)2 = 1× 4

∴ 4 = 4

Hence, h2 = ab is satisfied by the given equation so the equationx2 - 4xy + 4y2 = 0 are coincident to each other. Proved

Here,

ax2 + 2hxy + by2 = 0

When: h2 = ab then straight lines are coincident each other.

When: a + b = 0 then straight lines are perpendicular each other.

Given eqn of line are:

x = 2y

i.e. x - 2y = 0..........................(1)

2x = y

i.e. 2x - y = 0..........................(2)

Combined eqn of (1) and (2) is:

(x - 2y) (2x - y) = 0

or, 2x2- xy - 4xy + 2y2 = 0

or, 2x2 - 5xy + 2y2 = 0

∴ The required eqn is: 2x2 - 5xy + 2y2 = 0 Ans

Here,

Given eqn is: y2 = x2

or, x2 - y2 = 0

or, (x - y) (x + y) = 0

either: x + y = 0

Or, x - y = 0

Slope of eqn x + y = 0 is: m1 = -$$\frac 11$$ = -1

Slope of eqn x -y = 0 is: m2 = -$$\frac 1{-1}$$ = 1

m1× m2 = -1× 1 = -1

Hence, they are perpendicular to each other. Proved

Here,

Given eqn is:

6x2 - 5xy - 6y2 = 0...............................(1)

The eqnof homogenous is:

ax2 + 2hxy + by2 = 0..........................(2)

Comparing eqn (1) and (2)

a = 6

b = -6

Now,

a + b = 0

or, 6 - 6 = 0

∴ 0 = 0

Hence, the angle between two lines is 90°. Proved

Here,

Given eqn is:

x2 - 2xy sec$$\alpha$$ + y2 = 0...........................(1)

The homogenous eqn is:

ax2 + 2hxy + by2 = 0..............................(2)

Comparing eqn (1) and (2)

a = 1

h = - sec$$\alpha$$

b = 1

Now,

tan$$\theta$$ =± $$\frac {2\sqrt {h^2 - ab}}{a + b}$$

or, tan$$\theta$$ =± $$\frac {2\sqrt {(-sec\alpha)^2 - 1 × 1}}{1 + 1}$$

or, tan$$\theta$$ =± $$\frac {2\sqrt {sec^2\alpha - 1}}2$$

or, tan$$\theta$$ =± $$\sqrt {sec^2\alpha - 1}$$

or, tan$$\theta$$ =± $$\sqrt {tan^2\alpha}$$

or, tan$$\theta$$ =± tan$$\alpha$$

∴ $$\theta$$ = $$\alpha$$ Ans

Here,

Given eqn are:

x cos$$\alpha$$ + y sin$$\alpha$$ = 0...................(1)

x sin$$\alpha$$ + y cos$$\alpha$$ = 0...................(2)

Combined eqn of (1) and (2)

(x cos$$\alpha$$ + y sin$$\alpha$$) (x sin$$\alpha$$ + y cos$$\alpha$$) = 0

or, x2 cos$$\alpha$$.sin$$\alpha$$ +xy cos2$$\alpha$$ + xy sin2$$\alpha$$ + y2 sin$$\alpha$$.cos$$\alpha$$ = 0

or, x2 cos$$\alpha$$.sin$$\alpha$$ + y2 sin$$\alpha$$.cos$$\alpha$$ + xy (cos2$$\alpha$$ + sin2$$\alpha$$) = 0

or, sin$$\alpha$$.cos$$\alpha$$ (x2 + y2) + xy× 1 = 0

∴(x2 + y2) sin$$\alpha$$.cos$$\alpha$$ + xy = 0 Ans

Given equation is:

x2 + 4xy + y2 = 0.............................(1)

The homogeneous equation of second degree is:

ax2 + 2hxy + by2 = 0.....................(2)

Comparing (1) and (2)

a = 1

h =2

b = 1

Now,

tan$$\theta$$ = ± $$\frac {2\sqrt {h^2 - ab}}{a + b}$$

or, tan$$\theta$$ = ± $$\frac {2\sqrt {2^2 - 1 × 1}}{1 + 1}$$

or, tan$$\theta$$ = ± $$\frac {2\sqrt {4 - 1}}2$$

or, tan$$\theta$$ = ± $$\sqrt 3$$

∴ obtuse angle ($$\theta$$ = tan-1 (-$$\sqrt 3$$)

∴ $$\theta$$ = (90 + 30)° = 120°Ans

Here,

Given equation is:

3x2 + 2y2 - 5xy = 0

The homogeneous equation of second degree is:

ax2 + 2hxy + by2 = 0.....................(2)

Comparing (1) and (2)

a = 1

h =2

b = 1

Now,

tan$$\theta$$ = $$\frac {2\sqrt {h^2 - ab}}{a + b}$$

or, tan$$\theta$$ = $$\frac {2\sqrt {(\frac {-5}2)^2 - 3 × 2}}{3 + 2}$$

or, tan$$\theta$$ = $$\frac {2\sqrt {\frac {25}4 - \frac 61}}5$$

or, tan$$\theta$$ = $$\frac {2\sqrt {\frac {25 - 24}4}}5$$

or, tan$$\theta$$ = $$\frac {2 × \frac 12}{\frac 51}$$

or, tan$$\theta$$ = $$\frac 15$$

or, $$\theta$$ = tan-1($$\frac 15$$)

∴ $$\theta$$ = 11.31° Ans

Here,

The given equation is:

12x2 - 23xy + 5y2 = 0.....................(1)

The homogeneous equation of second degree is:

ax2 + 2hxy + by2 = 0.....................(2)

Comparing (1) and (2)

a =12

h = -$$\frac {23}2$$

b = 5

Now,

tan$$\theta$$ = ±$$\frac {2\sqrt {h^2 - ab}}{a + b}$$

or,tan$$\theta$$ = ± $$\frac {2\sqrt {(\frac {-23}2)^2 - 12 × 5}}{12 + 5}$$

or,tan$$\theta$$ = ± $$\frac {2\sqrt {\frac {529}4 - 60}}{17}$$

or,tan$$\theta$$ = ± $$\frac {2\sqrt {\frac {529 - 240}4}}{17}$$

or,tan$$\theta$$ = ± $$\frac {2\sqrt {289}}2$$× $$\frac 1{17}$$

or,tan$$\theta$$ = ± $$\frac {17}{17}$$

∴tan$$\theta$$ = ± 1

Taking +ve sign,

tan$$\theta$$ = 1

or, tan$$\theta$$ = tan 45°

∴ $$\theta$$ = 45°

Taking -ve sign,

tan$$\theta$$ = -1

or, tan$$\theta$$ = tan (180 - 35)

or, tan$$\theta$$ = tan 135°

∴ $$\theta$$ = 135°

Hence, the obtuse angle between the pair of equation is: 135°. Ans

Here,

The homogenous equation of second degree is:

ax2 + 2hxy +by2 = 0................................(1)

The given equation is:

2x2 - 5xy + 2y2 = 0...................................(2)

Comparing (1) and (2)

a = 2

2h = -5 i.e. h = -$$\frac 52$$

b = 2

If $$\theta$$ be the angle between pair of lines:

tan$$\theta$$ =± $$\frac {2\sqrt {h^2 - ab}}{a + b}$$

or, tan$$\theta$$ =± $$\frac {2\sqrt {(\frac {-5}2)^2 - 2 × 2}}{2 + 2}$$

or, tan$$\theta$$ =± $$\frac {2\sqrt {\frac {25}4 - \frac 41}}4$$

or, tan$$\theta$$ =± $$\frac {\sqrt {\frac {25 - 16}4}}2$$

or, tan$$\theta$$ =± $$\sqrt {\frac 94}$$× $$\frac 12$$

or, tan$$\theta$$ =± $$\frac 32$$× $$\frac 12$$

or, tan$$\theta$$ =± $$\frac 34$$

∴ $$\theta$$ = tan-1(± $$\frac 34$$)

Hence, the acute angle ($$\theta$$) =tan-1(± $$\frac 34$$) Ans

Here,

Given equation is:

6x2 + 5xy - 3x - 2y - 6y2 = 0

or, 6x2 + 9xy - 4xy - 6y2 - 3x - 2y = 0

or, 3x (2x + 3y) - 2y (2x + 3y) - 1 (2x + 3y) = 0

or, (2x + 3y) (3x - 2y - 1) = 0

Either: 2x + 3y = 0..........................(1)

Or: 3x - 2y - 1 = 0............................(2)

Slope of equation (1), m1 = -$$\frac 23$$

Slope of equation (2), m2 = $$\frac 32$$

Again,

m1× m2 = $$\frac {-2}3$$× $$\frac 32$$ = -1

The product of two slopes = -1

Hence, these equations are perpendicular each other. Hence, Proved

Here,

Let: the two equation of the lines through origin be:

a1x + b1y = 0..............................(1)

a2x + b2y = 0..............................(2)

Combined equation of (1) and (2) is:

(a1x + b1y) (a2x + b2y) = 0

or, a1a2x2 + a1b2xy + a2b1xy + b1b2y2 = 0

or,a1a2x2 + (a1b2+ a2b1)xy + b1b2y2 = 0

Let:

a1a2 = a

b1b2 = b

(a1b2+ a2b1) = 2h

Now,

ax2 + 2hxy + by2 = 0

Thus,ax2 + 2hxy + by2 = 0 is homogenous equation of second degree. Ans

Here,

The given equation is: ax2 + 2hxy + by2 = 0 if a≠ 0, then:

The given equation is multiplied by 'a' on both sides:

a2x2 + 2ahxy + aby2 = 0

or (ax)2 + 2 (ax) (hy) + (hy)2 - h2y2 + aby2 = 0

or, (ax + hy)2 - (h2 - ab) y2 = 0

or, (ax + hy)2 - {($$\sqrt {(h^2 - ab)y})}2 = 0 or, (ax + hy + \(\sqrt {(h^2 - ab)y}$$) (ax + hy - $$\sqrt {(h^2 - ab)y}$$) = 0

Either:(ax + hy + $$\sqrt {(h^2 - ab)y}$$) = 0.................(1)

Or:(ax + hy - $$\sqrt {(h^2 - ab)y}$$) = 0..........................(2)

Equation (1) and (2) are satisfied (0, 0) so both straight lines will passes through origin.

Again,

If a = 0

The equation ax2+ 2hxy + by2 = 0 will be

2hxy + by2 = 0

or, y(2hx + by) = 0

Either: y = 0.......................(3)

Or: 2hx + by = 0..............(4)

Equation (3) and (4) are satisfied by the co-ordinates (0, 0).

Hence, the second degree homogeneous equation: ax2 + 2hxy + by2 = 0 always represents a pair of straight lines through the origin. Proved

Here,

Given equationax2 + 2hxy + by2= 0 represents two straight lines that passes through the origin.

Let: y = m1x and y = m2x are the two lines.

y -m1x = 0............................(1)

y - m2x = 0............................(2)

Product of the equation (1) and (2) is:

(y - m1x) (y - m2x) = 0

or, m1m2x2 - m1xy - m2xy + y2 = 0

or, m1m2x2 - (m1 +m2)xy + y2 = 0...................(3)

Given equationax2 + 2hxy + by2= 0

$$\frac ab$$x2 + $$\frac {2h}b$$ xy + y2 = 0...................(4)

Comparing equation (3) and (4), we get:

m1 + m2 = -$$\frac {2h}b$$ and m1m2 = $$\frac ab$$

Let $$\theta$$ be the angle between the lines:

tan$$\theta$$ =± $$\frac {m_1 - m_2}{1 + m_1m_2}$$

or, tan$$\theta$$ =± $$\frac {\sqrt {(m_1 + m_2)^2 - 4m_1m_2}}{1 + m_1m_2}$$ [$$\because$$ a - b = $$\sqrt {(a + b)^2 - 4ab}$$]

or, tan$$\theta$$ =± $$\frac {\sqrt {\frac {4h^2}{b^2} - \frac {4a}b}}{1 + \frac ab}$$

or, tan$$\theta$$ =± $$\frac {\sqrt {\frac {4h^2 - 4ab}{b^2}}}{\frac {b + a}b}$$

or, tan$$\theta$$ =± $$\frac {2\sqrt {h^2 - ab}}{a + b}$$× $$\frac bb$$

or, tan$$\theta$$ =± $$\frac {2\sqrt {h^2 - ab}}{a + b}$$

∴$$\theta$$ = tan-1(± $$\frac {2\sqrt {h^2 - ab}}{a + b}$$) Ans

Here,

x2 - 5xy + 4y2 = 0

or, x2 - xy - 4xy + 4y2 = 0

or, x(x - y) - 4y(x - y) = 0

or, (x - y) (x - 4y) = 0

Either: x - y = 0.................(1)

Or: x - 4y = 0......................(2)

The eqn (1) changes into parallel form is:

x - y + k1 = 0......................(3)

The point (1, 1) passes through eqn (1)

1 - 1 + k1 = 0

∴ k1 = 0

Putting the value of k1 in eqn (3)

x - y + 0 = 0

x - y = 0............................(4)

The eqn(2) changes in parallel form is:

x - 4y + k2 = 0..................(5)

The point (1, 1) passes through eqn (5)

1 - 4× 1 + k2 = 0

or, -3 + k2 = 0

∴ k2 = 3

Putting the value of k2 in eqn (5)

x - 4y + 3 = 0.......................(6)

The eqn of pair of line is:

(x - y) (x - 4y + 3) = 0

or, x2 - 4xy + 3x - xy - 4y2 - 3y = 0

∴x2 - 5xy - 4y2 + 3x - 3y = 0Ans

Here,

Given equation is:

x2 - xy - 2y2 = 0

or, x2 - 2xy + xy - 2y2 = 0

or, x (x - 2y) + y (x - 2y) = 0

or, (x - 2y) (x + y) = 0

Either: x - 2y = 0.........................(1)

Or: x + y = 0.................................(2)

The eqn (1) changes in perpendicular form is:

-2x - y + k1 = 0

2x + y - k1 = 0..........................(3)

The eqn (3) passes through origin (0, 0):

2× 0 + 0 - k1 = 0

∴ k1 = 0

Putting the value of k1 in eqn (3)

2x + y - 0 = 0

2x + y = 0........................(4)

The eqn (2) change in perpendicular form is:

x - y + k2 = 0........................(5)

The eqn (5) passes through origin (0, 0)

0 - 0 + k2 = 0

∴ k2 = 0

Putting the value of k2 in eqn (5)

x - y + 0 = 0

x - y = 0...........................(6)

The equation of the pairs of lines is:

(2x + y) (x - y) = 0

or, 2x2 - 2xy + xy - y2 = 0

∴2x2 - xy - y2 = 0Ans

Given eqn of line is:

3x2 - 8xy + 5y2= 0

or, 3x2 - 3xy - 5xy + 5y2= 0

or, 3x (x - y) - 5y (x - y) = 0

or, (x - y) (3x - 5y) = 0

Either: x - y = 0.......................(1)

Or: 3x - 5y = 0.........................(2)

The eqn (1) changes in perpendicular form is:

x + y + k1 = 0...........................(3)

The point (2, 3) passes through eqn (3)

2 + 3 + k1 = 0

or, 5 + k1 = 0

∴ k1 = -5

Putting the value of k1 in eqn (3)

x + y - 5 = 0..........................(4)

The eqn (2) change in perpendicular form is:

5x + 3y + k2 = 0...................(5)

The point (2, 3) passes through eqn (5)

5× 2 + 3× 3 + k2 = 0

or, 10 + 9 + k2 = 0

or, 19 + k2 = 0

∴ k2 = - 19

Putting the value of k2 in eqn (5)

5x + 3y - 19 = 0......................(6)

The eqn of pairs of lines is:

(x + y - 5) (5x + 3y - 19) = 0

or, 5x2 + 3xy - 19x + 5xy + 3y2 - 19y - 25x - 15y + 95 = 0

∴ 5x2 + 8xy + 3y2 - 44x - 34y + 95 = 0Ans

Here,

x2 - xy - 2y2 = 0

or, x2 - 2xy + xy - 2y2 = 0

or, x(x - 2y) + y(x - 2y) = 0

or, (x - 2y) (x + y) = 0

Either: x - 2y = 0..................(1)

Or: x + y = 0...........................(2)

The eqn (1) change in perpendicular form is:

2x + y + k1 = 0.......................(3)

The point (3, -1) passes through eqn (3)

2× 3 - 1 + k1 = 0

or, 6 - 1 + k1 = 0

∴ k1= -5

Putting the value of k1 in eqn (3)

2x + y - 5 = 0..........................(4)

The eqn (2) change in perpendicular form is:

x - y + k2 = 0.........................(5)

The point (3, -1) passes througheqn (5)

3 + 1 + k2 = 0

∴ k2 = -4

Putting the value of k2 in eqn (5)

x - y - 4 = 0.........................(6)

The eqn of pair of lines is:

(2x + y - 5) (x - y - 4) = 0

or, 2x2 - 2xy - 8x + xy - y2 - 4y - 5x + 5y + 20 = 0

∴ 2x2 - xy- y2 - 13x + y + 20 = 0Ans

Here,

2x2 + 5xy + 3y2 = 0

or, 2x2 + 3xy + 2xy + 3y2 = 0

or, x(2x + 3y) + y(2x + 3y) = 0

or, (2x + 3y) (x + y) = 0

Either: 2x + 3y = 0

Or: x + y = 0

Given eqn is: 2x2 + 5xy + 3y2 = 0......................(1)

Homogenous eqn is: ax2 + 2hxy + by2 = 0...................(2)

Comparing eqn (1) and (2)

a = 2

h = $$\frac 52$$

b = 3

We know that:

tan$$\theta$$ =± $$\frac {2\sqrt {h^2 - ab}}{a + b}$$

or,tan$$\theta$$ =± $$\frac {2\sqrt {(\frac 52)^2 - 2 × 3}}{2 + 3}$$

or, tan$$\theta$$ =± $$\frac {2\sqrt {\frac {25}4 - 6}}5$$

or,tan$$\theta$$ =± $$\frac {2\sqrt {\frac {25 - 24}4}}5$$

or,tan$$\theta$$ =± $$\frac {2\sqrt {\frac 14}}5$$

or,tan$$\theta$$ =± $$\frac {2 × \frac 12}5$$

or,tan$$\theta$$ =± $$\frac 15$$

Taking +ve sign,

$$\theta$$ = tan-1 ($$\frac 15$$) = 11.31°

Taking -vesign,

$$\theta$$ = (180° - 11.31°) = 168.69°

∴ Required eqn are: 2x + 3y = 0 and x + y = 0 and angle between them are: 11.31° and 168.69°. Ans

Given eqn is:x2 + 2xy sec$$\theta$$ + y2 = 0........................(1)

Homogenous eqn is: ax2 + 2hxy + by2 = 0..........(2)

Comparingeqn(1) and (2)

a = 1

h = sec$$\theta$$

b = 1

If $$\alpha$$ be the angle between pairs of lines then,

tan$$\alpha$$ = $$\frac {2\sqrt {h^2 - ab}}{a + b}$$

or, tan$$\alpha$$ = $$\frac {2\sqrt {sec^2\theta - 1 × 1}}{1 + 1}$$

or, tan$$\alpha$$ = $$\frac {2\sqrt {sec^2\theta - 1}}2$$

or, tan$$\alpha$$ = $$\sqrt {tan^2\theta}$$

or, tan$$\alpha$$ = tan$$\theta$$

∴$$\alpha$$ = $$\theta$$ Proved

Again,

The given eqn is:

y2 + 2xy sec$$\theta$$ + x2 = 0..........................(3)

ax2 + bx + c = 0.............................(4)

Comparing (3) and (4)

a = 1

b = 2x sec$$\theta$$

c = x2

We know,

x = $$\frac {-b ± \sqrt {b^2 - 4ac}}{2a}$$

or, y = $$\frac {-(2x sec\theta) ± \sqrt {(2x sec\theta)^2 - 4 × 1 × x^2}}{2 × 1}$$

or, y = $$\frac {-2x sec\theta ± \sqrt {4x^2 sec^2\theta - 4x^2}}2$$

or, y = $$\frac {-2x sec\theta ± \sqrt {4x^2 (sec^2\theta - 1)}}2$$

or, y = $$\frac {-2x sec\theta ± 2x\sqrt {tan^2\theta}}2$$

or, y = $$\frac {-2x sec\theta ± 2x tan\theta}2$$

or, y = $$\frac {2(-x sec\theta ± xtan\theta)}2$$

or, y = - xsec$$\theta$$± x tan$$\theta$$

Taking +ve sign:

y = -xsec$$\theta$$ + xtan$$\theta$$

Taking -ve sign:

y = -xsec$$\theta$$ - xtan$$\theta$$

∴ The required eqn are:y = -xsec$$\theta$$ + xtan$$\theta$$ andy = -xsec$$\theta$$ - xtan$$\theta$$ Ans

Given equation is:x2 - 2xy cosec$$\theta$$ + y2 = 0.....................(1)

Homogenous equation is: ax2 + 2hxy + by2 = 0......................(2)

Comparing eqn (1) and (2)

a = 1

h = -cosec$$\theta$$

b = 1

If $$\alpha$$ be the angle between pair of lines then:

tan$$\alpha$$ =± $$\frac {2\sqrt {h^2 - ab}}{a + b}$$

or, tan$$\alpha$$ =± $$\frac {2\sqrt {(-cosec\theta)^2 - 1 × 1}}{1 + 1}$$

or, tan$$\alpha$$ =± $$\frac {2\sqrt {(-cosec\theta)^2 - 1}}2$$

or, tan$$\alpha$$ =± $$\frac {2\sqrt {cosec^2\theta - 1}}2$$

or, tan$$\alpha$$ =± $$\sqrt {cot^2\theta}$$

∴ tan$$\alpha$$ =± cot$$\theta$$

Taking +ve sign,

tan$$\alpha$$ = cot$$\theta$$

tan$$\alpha$$ = tan($$\frac p2$$ - $$\theta$$)

∴$$\alpha$$ = ($$\frac p2$$ - $$\theta$$)Hence, Proved

Here,

Given equation is:

2x2 + 7xy + 3y2 = 0

or, 2x2 + 6xy + xy + 3y2 = 0

or, 2x(x + 3y) + y(x + 3y) = 0

or, (x + 3y)(2x + y) = 0

The two equation represented by2x2 + 7xy + 3y2 = 0 are:

2x + y = 0......................(1)

x + 3y = 0......................(2)

Now,

Slope of equation (1), m1 = -$$\frac {x-coefficient}{y-coefficient}$$ = -2

Slope of equation (2),m2 =-$$\frac {x-coefficient}{y-coefficient}$$ = -$$\frac 13$$

If the angle between the lines be $$\theta$$ then:

tan$$\theta$$ =± $$\frac {m_1 - m_2}{1 + m_1m_2}$$

or, tan$$\theta$$ =± $$\frac {-2 + \frac 13}{1 + (-2) (-\frac 13)}$$

or, tan$$\theta$$ = ± $$\frac {\frac {-6 + 1}3}{\frac {3 + 2}3}$$

or, tan$$\theta$$ = ± $$\frac {-5}3$$× $$\frac 35$$

or, tan$$\theta$$ = ± 1

Taking +ve sign,

tan$$\theta$$ = tan 45°

∴ $$\theta$$ = 45°

Taking -ve sign,

tan$$\theta$$ = tan (180 - 45)° = tan 135°

∴ $$\theta$$ = 135°

∴ Required angles ($$\theta$$) = 45° and 135°Ans

The given equation is:

2x2 + 3xy - 2y2 = 0

or, 2x2 + 4xy - xy - 2y2 = 0

or, 2x(x + 2y) - y(x + 2y) = 0

or, (x + 2y) (2x - y) = 0

∴ Equation are: x + 2y = 0 and 2x - y = 0

Again,

2x2 + 3xy - 2y2 = 0............................(1)

The homogenous equation of second degree is:

ax2 + 2hxy + by2 = 0........................(2)

Comparingequation (1) and (2)

a = 2

h = $$\frac 32$$

b = -2

tan$$\theta$$ = $$\frac {2\sqrt {h^2 - ab}}{a + b}$$

or, tan$$\theta$$ = $$\frac {2\sqrt {(\frac 32)^2 - 2 × (-2)}}{2 + (-2)}$$

or, tan$$\theta$$ = $$\frac {2\sqrt {\frac 94 + \frac 41}}{2 - 2}$$

or, tan$$\theta$$ = $$\frac {2\sqrt {\frac {9 + 16}4}}0$$

or, tan$$\theta$$ =∞

∴ $$\theta$$ = tan-1∞ = 90°

∴ The required equations are: x + 2y = 0 and 2x - y = 0 and angle between the pairs of straight lines is 90°.Ans

Here,

Given equation is:

2x2- 3xy + y2 = 0......................(1)

The homogenous equation of second degree is:

ax2 + 2hxy + by2 = 0..................(2)

Comparing equation (1) and (2)

a = 2

h = -$$\frac 32$$

b =1

Now,

tan$$\theta$$ = ± $$\frac {2\sqrt {h^2 - ab}}{a + b}$$

or, tan$$\theta$$ = ± $$\frac {2\sqrt {(\frac {-3}2)^2 - 2 × 1}}{2 + 1}$$

or, tan$$\theta$$ = ± $$\frac {2\sqrt {\frac 94 - \frac 21}}3$$

or, tan$$\theta$$ = ± $$\frac {2\sqrt {\frac {9 - 8}4}}3$$

or, tan$$\theta$$ = ± $$\frac {2 × \frac 12}3$$

or, tan$$\theta$$ = ± $$\frac 13$$

For the obtuse angle,

tan$$\theta$$ = -$$\frac 13$$

$$\theta$$ = tan-1 ($$\frac 13$$)

Now,

2x2 - 3xy + y2 = 0

or, 2x2 - 2xy - xy + y2 = 0

or, 2x(x - y) - y(x - y) = 0

or, (x - y) (2x - y) = 0

∴ The required pairs of lines are: x - y = 0 and 2x - y = 0. Ans

Here,

6x2 + 5xy - 3x + 2y - 6y2 = 0

or, 6x2 + 5xy - 6y2 - 3x + 2y = 0

or, 6x2 + 9xy - 4xy - 6y2 - 3x + 2y = 0

or, 3x(2x + 3y) - 2y(2x + 3y) - 1(3x - 2y) = 0

or, (2x + 3y - 1) (3x - 2y) = 0

Either: 2x + 3y - 1 = 0...........(1)

Or: 3x - 2y = 0.........................(2)

Slope of equation (1), m1 = $$\frac {-3}{-2}$$ = $$\frac 32$$

Slope of equation (2),m2 = -$$\frac 23$$

∴ m1× m2 = $$\frac 32$$× $$\frac {-2}3$$ = -1

Hence, the product of two slopes = -1 so these equations are perpendicular to each other. Proved

The given equation is:

x2 - 2xy cosec$$\theta$$ + y2 = 0

or, (y)2 - (2x cosec$$\theta$$) y + (x)2 = 0..................(1)

ax2 + bx + c = 0......................(2)

Comparing (1) and (2)

a = 1

b = -2x cosec$$\theta$$

c = x2

x = $$\frac {-b ± \sqrt {b^2 - 4ac}}{2a}$$

y = -(-2x cosec$$\theta$$)± $$\frac {\sqrt {(-2x cosec\theta)^2 - 4(1) (x^2)}}{2× 1}$$

y = $$\frac {2x cosec\theta ± \sqrt {4x^2 cosec^2\theta - 4x^2}}2$$

y = $$\frac {2x cosec\theta ± 2x \sqrt {cosec^2\theta - 1}}2$$

y = $$\frac {2(x cosec\theta ± x cot\theta)}2$$

y = x cosec$$\theta$$± x cot$$\theta$$

The pair of lines are:

y - x (cosec$$\theta$$ - cot$$\theta$$) = 0 and

y - x (cosec$$\theta$$ + cot$$\theta$$) = 0

Comparing x2 -2xy cosec$$\theta$$ + y2 = 0 and ax2 + 2hxy + by2 = 0

a = 1

h = - cosec$$\theta$$

b = 1

We know that:

tanA =± $$\frac {2\sqrt {h^2 - ab}}{a + b}$$

or, tanA = ± $$\frac {2\sqrt {(-cosec\theta)^2 - 1 × 1}}{1 + 1}$$

or, tanA =± $$\frac {2\sqrt {cosec^2\theta - 1}}2$$

or, tanA =± cot$$\theta$$

∴ A = tan-1 (± cot$$\theta$$)

∴ The required equations are: y - x (cosec$$\theta$$ - cot$$\theta$$) = 0 and y - x (cosec$$\theta$$ + cot$$\theta$$) = 0 and angle (A) = tan-1 (± cot$$\theta$$). Ans