Question

What is the value of cos(150°)?

Answer 1

ANSWER

$-\frac{\sqrt[]{3}}{2}$

EXPLANATION

Given

$\begin{gathered} \cos \text{ 150} \\ \end{gathered}$

We can find cos 150 by using

$\begin{gathered} \cos (180-\theta)=-\cos \theta \\ \Rightarrow\cos (180-\theta) \\ =-\cos 30 \end{gathered}$

recall that

$\begin{gathered} \cos 30=\frac{\sqrt[]{3}}{2} \\ \end{gathered}$

Hence,

$\begin{gathered} \cos 150=-\cos 30 \\ =-\frac{\sqrt[]{3}}{2} \\ \end{gathered}$

Therefore, the value of cos 150 is

$-\frac{\sqrt[]{3}}{2}$