Question

Prove the following 1- sin A sin (90-1)/cot (90-a)= sin^2 A

Answer 1

Im going to assume its (90 - A) so we have:-

1 - sinA sin (90 - A) / cot (90 - A)

Convert to sines and cosines:-

= 1 - (sin A cos A) / cos ( 90 - A) / sin ( 90 - A)

= 1 - (sin A cos A) / sin A / cos A

= 1 - cos^2 A

= sin^2 A which is what is required.