Question

Please Answer this question see this image​

Answer 1

Answer:

1) cos 2b

Explanation:

cos (a+b) =0

=> cos (a+b) = cos 90

=> a+b = 90

=> a = 90- b

Now

sin(a+b)

= sin(90-b-b)

= sin(90-2b)

= cos 2b [as sin (90 - x) = cos x]