弧度制2π = 角度制360°
所以 弧度制1 =360°/(2π)=(180/π)°
角度制1°=2π/360=π/180 弧度制2π = 角度制360°
所以 弧度制1 =360°/(2π)=(180/π)°
角度制1°=2π/360=π/180