well, since we know that in π radians there are 180°, then how many radians in 150°?
[tex]\bf \begin{array}{ccll}
radians&de grees\\
\text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\
\pi &180\\
x&150
\end{array}\implies \cfrac{\pi }{x}=\cfrac{180}{150}\implies \cfrac{\pi \cdot 150}{180}\implies \stackrel{simplified}{\cfrac{5\pi }{6}}[/tex]
