# Problem of trigonometry

Hello,

I have a big problem of trigonometry, I want to convert the yaw of my robot from quaternion to radians using GetYaw() function, it's working pretty well, but I still have a problem.

I am using cos and sin functions but the robot orientation is now in radians but it's going from -pi to +pi, why wont it be like any normal trigonometric circle, from 0 to 2pi ?

Here there a way to change that ? Im pretty stuck at the moment and my brain is smelting, thank you in advance !