cos^2(4)theta+sin^2(4)tetha

Question

what is this expression equivalent too?? 1)1 2)2 3)costheta 4)cos8tetha

Answer 1

sin²x + cos²x = 1 is a trigonometric identity, or definition.

 

This identity holds for any two angles that are equal, regardless of what quadrant they lie in. Multiples of the angles, i.e. (nx) for all x within the real number system, will always be equal. 

 

sin²(8x) + cos²(8x) = 1 follows directly from the trigonometric identity.