Q.
If β is one of the angles between the normals to the ellipse, x2+3y2=9 at the points (3cosθ,3sinθ) and (−3sinθ,3cosθ);θϵ(0,2π); then sin2θ2cotβ is equal to
2xdx+6ydy=0 2xdx=−cydy −dydx=x3y =stepe of normal m1=3cosθ33sinθ=3tanθ m2=−3sinθ33cosθ−3cotθ tanβ=[1+(3tanθ)(−3cotθ)3tanθ+3cotθ] tanβ=3(∣1−3tanθ+cotθ) =23(tanθ+cotθ) We have to find =sin2θ2cotβ −3(tanθ+cotθ)2sinθcosθ22 =3(cosθsinθ+sinθcosθ)sinθcosθ2 =32