We will have the following:
First, we know that a whole rotation is 360°, so we can see that the number of rotations that are take are 2:
[tex]\begin{cases}360\cdot2=720 \\ \\ 360\cdot3=1080\end{cases}[/tex]
So, we find the remaining angle:
[tex]1020-720=300[/tex]
So, we transform that to radians:
[tex]300\cdot\frac{\pi}{180}=\frac{5}{3}\pi[/tex]
So, the coterminal angle to 1020° is 300° which in radians is:
[tex]\frac{5\pi}{3}[/tex]
