we know that if x and y are complementary then x+y=90°-------> y=90-x and sin(y)=sin(90-x) remember---------> sin(A-B)=sin A cos B - cos A sin B sin(90-x)=sin 90 cos x - cos 90 sin x sin(90-x)=(1)* cos x - (0)* sin x-----------> cos(x) therefore sin(y)=cos (x)
the answer is the option C). No, cos X = sin Y if X and Y are complementary angles
