VectorToRad- From a vector returns the angle in radians

Function that returns the angle expressed in radians of a vector. - VectorToRad(X1,Y1,X2,Y2): float Parameters: - (int) X1: X coordinate of the vector's starting point; - (int) Y1: the Y coordinate of the vector's starting point; - (int) X2: X coordinate of the vector's ending point; - (int) Y2: the Y coordinate of the vector's ending point. Description: Use the VectorToRad function to derive the angle expressed in radians of a vector. The vector is given by two points, two pairs of coordinates that indicate the starting and ending point of the vector.