Return angle(in radians) between x, y and coordinate system passing through central point assuming Y-axis is from bottom to top, X-axis is from left to right, and angle is measured from X axis to Y-axis(angle 0 means the point is on the X axis and x is positive; angle PI/2 means the point is on the Y axis and y is positive; and so on). distance is the distance between x, y and center_x, center_y points. The function is only available for floating point data types.

You can find more information in comments below.

template<class TYPE>
    typename std::enable_if<std::is_floating_point<TYPE>::value, TYPE>::type Angle(const TYPE x, const TYPE y, const TYPE center_x, const TYPE center_y);
    
    template<class TYPE>
    typename std::enable_if<std::is_floating_point<TYPE>::value, TYPE>::type Angle(const TYPE x, const TYPE y, const TYPE center_x, const TYPE center_y, const TYPE distance);