Answer
$\frac{-20\pi}{9}\text{radians}.$
Work Step by Step
To convert from degrees to radians, the answer in degrees must be multiplied by $\frac{\pi}{180^\circ}$.
Therefore:
$-400^\circ=-400\cdot\frac{\pi}{180^\circ}\text{radians}=\frac{-20\pi}{9}\text{radians}.$
