Trigonometry Question (Trigonometric Functions)

[MarcZZ]

Homework Statement

Hello again, not looking for anyone to solve this problem this time I just need to know what the operation I'm supposed to do is called, so I can go research it and learn it.

If sin(t) = -12/13 with 3pi/2 < t < 2pi, find the following:

b) cos(t - 11pi/6)

Homework Equations

I'm assuming this is a trigonometric function that is about graphing these things. But I'm not sure. >_<

The Attempt at a Solution

As I said, I'm not looking for the solution. Just what kind of operation this is.

 

[eumyang]

Use sin²x + cos²x = 1 to find cos(t). Then, use the cosine of a difference identity to evaluate cos(t - 11pi/6).

 

[MarcZZ]

Oh, it's a sum and difference equation. My bad. I will go work on this now...