6.5 Average Value of a Function/2

$f(x)=\sin {(4x)}{\text{,}}\quad [-\pi ,\pi ]$

Failed to parse (Conversion error. Server ("https://en.wikipedia.org/api/rest_") reported: "Cannot get mml. Server problem."): {\displaystyle f_{avg}={\frac {1}{\pi -(-\pi )}}\int _{-\pi }^{\pi }\sin {(4x)}\,dx}