##plotting a triangle

#let the corner opposite "c" be at 0,0
ax <- 0
ay <- 0
#let the line from that corner to the point opposite "a" be along the x-axis
##this is just the side labeled "b" and is that length

bx<-tr1@b
by<-0

##now to find the third corner -- opposite the side labeled "b"
#this has length a and has one end at the origin and the other
##at x= a cos(theta)
##   y= a sin(theta)
## where theta is angleC

cx <- tr1@a * cos(angleC(tr1))
cy <- tr1@a * sin(angleC(tr1))

xpos<-c(ax,bx,cx,ax)
ypos<-c(ay,by,cy,ay)

plot(xpos,ypos)

##now use segments:
s<-1:3
segments(xpos[s],ypos[s], xpos[s+1], ypos[s+1])