Straight lines

If θ1 and θ2 be the angles which the lines (x2+y2)(cos2 θ sin2α+ sin2θ)= (x tanθ - y sinθ)2 make with the x axis and θ= π/6 , then what is the value of (tan θ1+ tan θ2) ?

answer:(-8/3 cosec 2α)

3 Answers

62
Lokesh Verma ·

(x2+y2)(cos2 θ sin2α+ sin2θ)= (x tanθ - y sinθ)2

thus,

(x2+y2)(cot2 θ sin2α+ 1)= (x secθ - y)2

(x2+y2)(cot2 θ sin2α) +(x2+y2) = x2sec2θ + y2 - 2xysecθ

thus,

(x2+y2)(cot2 θ sin2α) = x2tan2θ - 2xysecθ

thus,

(x2+y2)(3sin2α) = x2/3 - 4/√3 xy

3sin2αx2+3sin2α y2 = x2/3 - 4/√3 xy

now this is a quadratic in m

y/x=mm

then,
3sin2α m2 + 4/√3m + 3sin2α -1/3 = 0

we have to find m1 + m2 = -4/(3√3) cosec2α

I dont know where i am going wrong :(

1
satan92 ·

I am also etting the same answer

62
Lokesh Verma ·

hmm.. so we are correct :)

Your Answer

Close [X]