# atan2(3m) [ultrix man page]

sin(3m) sin(3m)Namesin, cos, tan, asin, acos, atan, atan2 - trigonometric functions and their inversesSyntax#include <math.h> double sin(x) double x; float fsin(x) float x; double cos(x) double x; float fcos(x) float x; double tan(x) double x; float ftan(x) float x; double asin(x) double x; float fasin(x) float x; double acos(x) double x; float facos(x) float x; double atan(x) double x; float fatan(x) float x; double atan2(y,x) double y,x; float fatan2(y,x) float y,x;DescriptionThe and functions return trigonometric functions of radian arguments x for double data types. The and functions return trigonometric functions for float data types. The and functions return the arc sine in the range -pi/2 to pi/2 for double and float data types, respectively. The and functions return the arc cosine in the range 0 to pi for double and float data types, respectively. The and functions return the arc tangent in the range -pi/2 to pi/2 for double and float data types, respectively. The and functions return the arc tangent of y/x in the rangeto using the signs of both arguments to determine the quadrant of the return value for double and float data types, respectively. Error (due to roundoff) When P stands for the number stored in the computer in place of pi = 3.14159 26535 89793 23846 26433 ... . and "trig" stands for one of "sin", "cos" or "tan", then the expression "trig(x)" in a program actually produces an approximation to trig(x*pi/P), and "atrig(x)" approximates (P/pi)*atrig(x). The approximations are close. P differs from pi by a fraction of an ulp; the difference is apparent only if the argument x is huge, and even then the difference is likely to be swamped by the uncertainty in x. Every trigonometric identity that does not involve pi explicitly is satisfied equally well regardless of whether P = pi. For example, sin(x)**2+cos(x)**2 = 1 and sin(2x) = 2sin(x)cos(x) to within a few ulps regardless of how big x is. Therefore, the difference between P and pi is unlikely to effect scientific and engineering computations.-piReturn ValuesAll the double functions return NaN if NaN is passed in. If |x| > 1 then (x) and (x) will return the default quiet NaN. The function defines (0,0) = NaN.See Alsohypot(3m), math(3m), sqrt(3m) RISC sin(3m)

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Namesin, cos, tan, asin, acos, atan, atan2 - trigonometric functions and their inversesSyntax#include <math.h> double sin(x) double x; float fsin(x) float x; double cos(x) double x; float fcos(x) float x; double tan(x) double x; float ftan(x) float x; double asin(x) double x; float fasin(x) float x; double acos(x) double x; float facos(x) float x; double atan(x) double x; float fatan(x) float x; double atan2(y,x) double y,x; float fatan2(y,x) float y,x;DescriptionThe and functions return trigonometric functions of radian arguments x for double data types. The and functions return trigonometric functions for float data types. The and functions return the arc sine in the range -pi/2 to pi/2 for double and float data types, respectively. The and functions return the arc cosine in the range 0 to pi for double and float data types, respectively. The and functions return the arc tangent in the range -pi/2 to pi/2 for double and float data types, respectively. The and functions return the arc tangent of y/x in the rangeto using the signs of both arguments to determine the quadrant of the return value for double and float data types, respectively. Error (due to roundoff) When P stands for the number stored in the computer in place of pi = 3.14159 26535 89793 23846 26433 ... . and "trig" stands for one of "sin", "cos" or "tan", then the expression "trig(x)" in a program actually produces an approximation to trig(x*pi/P), and "atrig(x)" approximates (P/pi)*atrig(x). The approximations are close. P differs from pi by a fraction of an ulp; the difference is apparent only if the argument x is huge, and even then the difference is likely to be swamped by the uncertainty in x. Every trigonometric identity that does not involve pi explicitly is satisfied equally well regardless of whether P = pi. For example, sin(x)**2+cos(x)**2 = 1 and sin(2x) = 2sin(x)cos(x) to within a few ulps regardless of how big x is. Therefore, the difference between P and pi is unlikely to effect scientific and engineering computations.-piReturn ValuesAll the double functions return NaN if NaN is passed in. If |x| > 1 then (x) and (x) will return the default quiet NaN. The function defines (0,0) = NaN.See Alsohypot(3m), math(3m), sqrt(3m) RISC sin(3m)