#====================
# Figure 9.2.R.
# Picture of two similar right triangles.
#====================
y=0
x=0
plot(x,y,type="l",lty=0,axes=FALSE,ann=FALSE,xlim=c(-1,1),ylim=c(-1,1))
th=4*pi/18
x0=c(0,cos(th),cos(th))
y0=c(0,sin(th),0)
x1=c(cos(th),cos(th),0)
y1=c(sin(th),0,0)
segments(x0,y0,x1,y1,lwd=2)
s=.08
a0=c(cos(th)-s,cos(th)-s)
a1=c(cos(th)-s,cos(th))
b0=c(0,s)
b1=c(s,s)
segments(a0,b0,a1,b1)

r=.5
x2=c(-1,r*cos(th)-1,r*cos(th)-1)
y2=c(0,r*sin(th),0)
x3=c(r*cos(th)-1,r*cos(th)-1,-1)
y3=c(r*sin(th),0,0)
segments(x2,y2,x3,y3,lwd=2)
c0=c(r*cos(th)-1-s,r*cos(th)-1-s)
c1=c(r*cos(th)-1-s,r*cos(th)-1)
d0=c(0,s)
d1=c(s,s)
segments(c0,d0,c1,d1)

text(.6*cos(th),-.1,expression(italic(x)),cex=1.5)
text(cos(th)+.1,.4*sin(th),expression(italic(y)),cex=1.5)
text(cos(th)/2,.4,expression(italic(r)),cex=1.5)
text(.3*cos(th),.1,expression(theta),cex=1.5)

text(-.8,-.1,expression(italic(v)),cex=1.5)
text(r*cos(th)-1+.1,.2*sin(th),expression(italic(w)),cex=1.5)
text(-.85,.25,expression(italic(q)),cex=1.5)

text(.25*cos(th)-1,.08,expression(theta),cex=1.5)