If $\cos \theta + \sec \theta = 2$, then the value of $\sin^ 6 \theta + \cos^ 6 \theta$ is:
Answer & explanation
Correct answer: option 3
We are given that :-
cosθ + secθ= 2
cosθ + \(\frac{1}{cosθ}\) = 2
cos²θ - 2cosθ + 1 = 0
cos²θ - cosθ - cosθ + 1 = 0
cosθ ( cosθ - 1 ) - 1 ( cosθ - 1 ) = 0
( cosθ - 1 )² = 0
cosθ = 1
{ we know, cos 0º = 1 }
So, θ = 0º
Now,
sin6 θ + cos6 θ
= sin6 0º + cos6 0º
= 1