Question

cos90-A=0 thn sinA+B=?​

Answer 1

Answer:

cos(α+β)=0

⇒cos(α+β)=cos90(∵cos0=0)

⇒α+β=90

⇒α=90−β

sin(α−β)

=sin(90−2β)=cos2β (∵sin(90−θ)=cosθ)