# Trigonometry Angle Addition and Subtraction

I'm working on a problem.

The problem is boxed in Blue. Ignore the right side boxed in green, it's unreleated. Inside the blue box, I have highlighted in green where my error is when solving this problem.

This problem is from a website, and I'm a little confused, as to why my answer (boxed in red) is wrong. I've used Desmos.com and my answer is indeed wrong. It seems that I'm not understanding how the + and - signs are working? to get the first part of my answer inside of the error box I used the special angle identities.

Thanks in advance for any input.

• $\sin(30^o)=1/2$ and $\cos(30^o=\sqrt{3}/2)$ – Rohit Gupta May 29 at 19:14
• This is not legible, at least not by me. Please type your questions. – saulspatz May 29 at 19:15
• @pBlack Now that you know what your mistake was, you may respond to your own question. This tutorial explains how to typeset mathematics on this site. – N. F. Taussig May 29 at 19:55