Help with how to solve this!!

[Excale]

Can someone help me with this problem I am having I keep getting an error message and don't know what I am doing wrong. Here is a screen shot of the problem.
Thank you in advance.

Chap 2 problem.jpg

[Levak]

Put the square after the parenthesis.
Indeed, tan, sin and cos are functions, which means they need the opening parenthesis to follow by the function name.

In other words, instead of doing tan^2(120), do tan(120)^2, and same for others.

[randall weidner]

I tried that and it gave me an answer of 45/4 and the correct answer I found out was 51/4 but I still don't know how to get to that answer.

[Bisam]

You "correct" answer is wrong !

$mathjax$\cos(90°)=0$mathjax$

,

$mathjax$\sin(150°)=\frac{1}{2}$mathjax$

and

$mathjax$\tan(120°)=-\sqrt{3}$mathjax$

Hence,

$mathjax$4\tan^2(120°)-3\sin^2(150°)-\cos^2(90°)=4\times 3-3\times\frac{1}{4}-0=\frac{48-3}{4}=\frac{45}{4}$mathjax$