Question

(CosAcosB+sinAsinB)²+(sinAcosB-cosAsinB)²=1

Answer 1

[cos(A-B)]² + [sin(A-B)]² = 1

Because cos (A-B) = cos A cos B + sin A sin B
and sin(A-B) = sin A cos B + cos A sin B

Answer 2

Refer attachment

☺ Hope this Helps ☺