There are pi radians in 180 degrees.
radians = degrees * (pi/180)
So, to convert a degree into radians you basically just multiply pi/180 to the degree, then simplify to get the radian measure .
-135 degrees=-135*pi/180 radians =-(3/4)pi radians
-25 degrees=-25*pi/180 radians = -(5/36)pi radians
-115 degrees=-115*pi/180 radians =-(23/36)pi radians
-225 degrees=-225*pi/180 radians =-(5/4)pi radians