.\" sin.pic -- sin function
.\" $Id$
.\" Carlos Duarte, 971126/981016
.\"
.PS
# call: do_sin(width), plots a sin funcion, with a period (or a 
# total horizontal measure), of `width'
# 
define do_sin { [
	old_y = 0
	old_x = 0
	pi = atan2(0,-1)
	for t = 0 to $1 by .025 do {
		y = .8*sin(2*pi*t/$1)
		x = .4*2*pi*t/$1
		spline right x-old_x up y-old_y
		old_y = y
		old_x = x
	}
] }

# usage: 
line -> right 2.6
line -> up 1.6 at last line.c - (0,1.6/2)
do_sin(4) with .c at last line.center
box dashed wid last [].wid+.2 ht last [].ht+.2 with .c at last [].c
"sin(t)" at last box .s - (0,0.2)
.PE