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atan2
Four-quadrant inverse tangent
P = atan2(Y,X)
P = atan2(Y,X)
returns an array P the same size as X and Y containing the element-by-element, four-quadrant inverse tangent (arctangent) of the real parts of Y and X. Any imaginary parts are ignored.
Elements of P lie in the half-open interval 
. The specific quadrant is determined by sign(Y) and sign(X):
atan(Y/X), which is limited to the interval 
, or the right side of this diagram.
Any complex number z = x+iy is converted to polar coordinates with
r = abs(z)
theta = atan2(imag(z),real(z))
To convert back to the original complex number:
z = r *exp(i *theta)This is a common operation, so MATLAB provides a function,
angle(z), that simply computes atan2(imag(z),real(z)).
atan, atanh Inverse tangent and inverse hyperbolic tangent
tan, tanh Tangent and hyperbolic tangent