.\" triangle.pic -- draw triangles
.\" $Id$
.\" Carlos Duarte, 971122
.\"
.PS
# draw an equilateral triangle
# call: eq_tri(size_dimension)
# 
define eq_tri { [
	side = $1
	line right side \
	  then up sqrt(3)*side/2 left side/2 \
	  then down sqrt(3)*side/2 left side/2
] }

# general triangle
# call: tri(a,b,c)
#
define tri { [
	a = $1
	b = $2
	c = $3
	cos_a = (a*a-b*b-c*c)/(2*b*c)
	sin_a = (1-cos_a*cos_a)
	line right a
	if (cos_a == 0) then {
		line from last line .start right (b*cos_a) up (b*sin_a)
	} else {
		line from last line .start right (b*sin_a) up (b*cos_a)
	}
	line from last line .end to 2nd last line .end
] }

# rectangle triangle
# call: r_tri(1,2)
define r_tri { [
	line down $1
	line right $2
	line from last line .end to 2nd last line .start
] }

scale=2

eq_tri(1);	move down from last [].c
tri(1,2,3);	move down from last [].c
tri(2,3,4);	move down from last [].c
tri(4,1,2);	move down from last [].c
r_tri(1,2);	move down from last [].c
r_tri(2,1);	move down from last [].c

.PE