The php Function Atan2

The php function atan2 is used to get the arc tangent of two numbers. This is the angle corresponding to a point (x, y) in the Cartesian coordinate system. The value of atan2 is returned in radians and can be converted to degrees using the DEGREES function. Computer programming languages often use different values for atan2 depending on their implementation and conventions. For example, some systems treat the order of the arguments as reversed, while others do not.

Aside from its basic function, atan2 is a key building block in differential geometry, since it yields the first de Rham cohomology of the punctured plane. It is also useful in many applications involving Euclidean vectors, for example, finding the direction of a vector from one point to another or converting a rotation matrix to Euler angles.

It is a special case of the general inverse tangent function, where a scalar argument is multiplied by an argument of the same type. It is therefore equal to the inverse of the cosine function, which is the sine of the scalar argument divided by the square root of that same number.

The atan2 function is sometimes referred to as the arc tangent of x and y or four-quadrant inverse tangent, since it uses the signs of x and y to determine the quadrant in which the result will lie. This is an important distinction from a simple arc tangent, which only considers the magnitude of the angle and does not take sign into account.