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+.TH SIN 2
+.SH NAME
+sin, cos, tan, asin, acos, atan, atan2 \- trigonometric functions
+.SH SYNOPSIS
+.B #include <u.h>
+.br
+.B #include <libc.h>
+.PP
+.B
+double sin(double x)
+.PP
+.B
+double cos(double x)
+.PP
+.B
+double tan(double x)
+.PP
+.B
+double asin(double x)
+.PP
+.B
+double acos(double x)
+.PP
+.B
+double atan(double x)
+.PP
+.B
+double atan2(double y, double x)
+.SH DESCRIPTION
+.I Sin, cos
+and
+.I tan
+return trigonometric functions of radian arguments.
+The magnitude of the argument should be checked
+by the caller to make sure the result is meaningful.
+.PP
+.I Asin
+returns the arc sine in the range
+\-π/2 to π/2.
+.PP
+.I Acos
+returns the arc cosine in the range
+0 to π.
+.PP
+.I Atan
+returns the arc tangent in the range
+\-π/2 to π/2.
+.PP
+.I Atan2
+returns the arc tangent of
+.I y/x
+in the range
+\-π to π.
+.SH SOURCE
+.B /sys/src/libc/port
+.SH SEE ALSO
+.IR intro (2)
+.SH BUGS
+The value of
+.I tan
+for arguments greater than about
+.if t 2\u\s-231\s+2\d
+.if n 2^31
+is garbage.