Question

if cos(a+b) = 0,then sin (a-b) can be reduced to: 1.cosb 2. 2cosb 3.sina 4.2sina​

Answer 1

Answer:

cos(a+b) = 0

this implies a + b = 90

a = 90 - b

put this in sin (a-b)

we get

sin( 90-b-b) = sin(90-2b) = cos2b

thus the answer is cos2b....