[Syntax]
double atan2(double y, double x)
float atan2f(float y, float x)
long double atan2l(long double y, long double x) [V2.01.00 or later]
[Description]
These functions calculate the arc tangent of y/x.
[Special case]
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x==0, y==0
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NaN
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EDOM
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x==±∞, y==±∞
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NaN
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EDOM
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Underflow occurred
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±0
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ERANGE
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x<0, y==0
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π
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-
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x==0
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±π/2
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-
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