Question

What is the value of cos(150°)?

Answer 1

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

Step-by-step 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}`