Unidentified constant value im working on the following project kalman filter

and im working to implement in arduino.. i read the entire code and i succesfully implemented it into arduino but i couldnt implement the following function code line because arduino gives "not defined" error in PI_DIV_180

imu_MadgwickQuaternionUpdate(bUseAccel,elapsedTimeSecs,fax,fay,faz,fgx*PI_DIV_180,fgy*PI_DIV_180,fgz*PI_DIV_180,fmx,fmy,fmz);


it multiplies fgx with PI_DIV_180 but as i said arduino cant identify it

i looked into math.h to find the value of that define but there isnt anything in math.h related with this

the imu_MadgwickQuaternionUpdate function is in here IMU.cpp

can anyone help me please thanx..
Maybe it's pi (π) divided by 180?

Pi is roughly: 3.1415926535898

So:

3.1415926535898 / 180 = 0.017453292519943


So add this line:

#define PI_DIV_180 0.017453292519943