How do you identify if you should you sine, cosine, of tangent

Well, you use an identity that includes "x", and the angle, and some other value provided there.

now, we have "x" the opposite side, we also know the angle, is 60°, and we know the hypotenuse is 17.

we can't use the cosine, because we don't have the adjacent one, to use the tangent, we'd need the adjacent as well, so no dice there either.

but low and behold, sine uses the hypotenuse and the opposite, let's try that one,

 

make sure your calculator is in Degree mode.