"Find expressions for sin(A) and cos(A) where A is an 18 degree angle. Hint: A nice way I saw in an old trigonometry book is to note that 2A is the complement of 3A, so sin(2A)=cos(3A)"

I know 2A= 36 degrees, and 3A= 54 degrees, so sin(36)=cos(54).

Can someone walk me through this problem and explain to me what I have to do? I thought at first I would use a double angle formula, but the hint really threw me off, and now I'm not sure.

Question

"Find expressions for sin(A) and cos(A) where A is an 18 degree angle. Hint: A nice way I saw in an old trigonometry book is to note that 2A is the complement of 3A, so sin(2A)=cos(3A)"

I know 2A= 36 degrees, and 3A= 54 degrees, so sin(36)=cos(54). 

Can someone walk me through this problem and explain to me what I have to do? I thought at first I would use a double angle formula, but the hint really threw me off, and now I'm not sure.