V9/jtools/man/man3/cos.3

.TH COS 3
.CT 2 math
.SH NAME
cos, sin, atan2, sqrt, norm \- integer math functions
.SH SYNOPSIS
.B int cos(d)
.B int d;
.PP
.B int sin(d)
.B int d;
.PP
.B int atan2(x, y)
.B int x, y;
.PP
.B int norm(x, y, z)
.B int x, y, z;
.PP
.B int sqrt(x)
.B long x;
.PP
.SH DESCRIPTION
.I Cos
and
.I sin
return scaled integer approximations to the trigonometric functions.
The argument values are in degrees.
The return values are scaled so that
.BR cos(0)==1024 .
Thus, to calculate the mathematical expression
.if t .IR x \|=\| a\^ cos( d ),
.if n .IR x = x0 *cos( d ),
the multiplication must be scaled:
.IP
.L
x = muldiv(x0, cos(d), 1024)
.PP
.I Atan2
returns the approximate arc-tangent of
.IR  y / x .
The return value is in integral degrees.
.PP
.I Sqrt
returns the 16-bit signed integer closest to the
square root of its 32-bit signed argument.
.PP
.I Norm
returns the Euclidean length of the three-vector
.RI ( x ,
.IR y ,
.IR z ).
.SH DIAGNOSTICS
.I Sqrt
returns 0 for negative arguments; and
.BR atan2(0,0)==0.
.IR Norm
does not protect against overflow.
.SH BUGS
.I Atan2
may be off by as much as two degrees.