If 2 sin2θ + 3 cosθ = 3, 0o < θ < 90o, then the value of (sec2θ +cot2 θ) is
Answer & explanation
Correct answer: option 3
We are given that :-
2 sin²θ + 3 cosθ = 3
{ we know, sin²θ + cos²θ = 1 }
2 ( 1 - cos²θ ) + 3 cosθ = 3
2 - 2cos²θ + 3 cosθ = 3
2cos²θ - 3 cosθ + 1 = 0
2cos²θ - 2 cosθ - cosθ + 1 = 0
2 cosθ ( cosθ - 1 ) - 1 ( cosθ - 1 ) = 0
( 2cosθ - 1 ) . ( cosθ - 1 ) = 0
( cosθ - 1 ) = 0 is not possible because 0º < θ < 90º
So, 2cosθ - 1 = 0
cosθ = \(\frac{1}{2}\)
{ we know, cos60º = \(\frac{1}{2}\) }
So, θ = 60º
Now,
( sec ²θ + cot ²θ )
= ( sec ²60º + cot ²60º )
= 4 + \(\frac{1}{3}\)
= 4\(\frac{1}{3}\)