# Easy Trig question Help me plz

posted by
**John** on
.

can someone tell me the steps of answering this problem Sin(B+15)=Cos(2B+30) the answer is B=15 but im not sure how to get that answer, i thought u set B+15=2B+30 but i end up getting B= -15 when i do that.

You should know the basic relation between sine and cosine is

sin(x)=cos(90 -x) Thus

B+15 = 90 - (2B+30) so

3B +45 = 90 or

3B = 45 and B =45/3

No, you cannot just set them equal to each other.