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These are the usual arc sine, arc cosine and arc tangent functions, which are the inverses of the sine, cosine and tangent functions, respectively.
-pi/2
and pi/2
(inclusive).
asin
fails, and sets errno
to EDOM
, if x is
out of range. The arc sine function is defined mathematically only
over the domain -1
to 1
.
0
and pi
(inclusive).
acos
fails, and sets errno
to EDOM
, if x is
out of range. The arc cosine function is defined mathematically only
over the domain -1
to 1
.
-pi/2
and pi/2
(inclusive).
-pi
to pi
, inclusive.
If x and y are coordinates of a point in the plane,
atan2
returns the signed angle between the line from the origin
to that point and the x-axis. Thus, atan2
is useful for
converting Cartesian coordinates to polar coordinates. (To compute the
radial coordinate, use hypot
; see section Exponentiation and Logarithms.)
The function atan2
sets errno
to EDOM
if both
x and y are zero; the return value is not defined in this
case.
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