Question

If sin A – cos A = 0, then the value of sin4 A + cos4 A is

Answer 1

.

From the above equation, we get

cosθ=sinθ

Hence

θ=45

Therefore

sin 4θ+cos 4θ=sin 445 0+cos4 45 0

=2×(21) 4

=2× 41

= 21