Convert an angle from degrees to radians with exact fractional-pi form when possible.
To convert degrees to radians, multiply by π/180. Common angles have exact fractional-pi forms: 90° = π/2, 60° = π/3, 45° = π/4, 30° = π/6.
Degree to Radian
radians = degrees × π / 180
Radians are the natural unit in calculus and physics. The derivative of sin(x) is cos(x) only when x is in radians. One radian is the angle subtended by an arc equal in length to the radius.
2π radians = 360°. So π radians = 180°, and 1 radian ≈ 57.2958°.