Question

PLEASE HELP. Is this correct? cos(90 +Q ) = -sinQ PLEASE HELP. Is this correct? cos(90 +Q ) = -sinQ @Mathematics

Answer 1

Yes..

Answer 2

Yes, it is. And you can prove it using the identity:

cos(x + y) = cos x . cos y - sin x . sin y

With x = 90 and y = Q, we have

cos(90 + Q) = cos 90 . cos Q - sin 90 . sin Q
= 0 . cos Q - 1 . sin Q
= - sin Q

Answer 3

Thanks!