If sinx=−1/2, and 270°<x<360°, what is cos(x−30°)?

Question

Enter your answer as a fraction in simplest form, like this: 3/14

Help please I need take this exam.;

Answer 1

Use the formula for the cosine of the difference of 2 angles.

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