Question

if cos (a+b)=0 Then sin (a-b) can be reduced to
A cos b
B. cos2b
C. sin a
D. sin2a​

Answer 1

I hope this will surely help you mate

Answer 2

cos(a+b)=0

cos(a+b)=90               (because cos 0=90)

that means , a+b =90 or a=90-b

putting it in sin (a-b),

  therefore,  sin (a-b) =  sin (90-b-b) =  sin (90-2b)

now, let ∅= 2b

sin (90-2b) = sin (90-∅)

sin (90-∅) = cos ∅

      therefore, cos2b .   is the right answer.