code for diagram

> slants:=plot({[[0,0],[1.5,1 ]], [[2,1],[3.5,0]]}, thickness=3,color=blue,scaling=constrained,xtickmarks=[],
ytickmarks=[], axes=none):
base:=plot([[0,0],[3.5,0]], thickness=2, linestyle=3):
connectors:=plot({[[1.5,1 ],[2,1]],[[1.5,1 ],[1.5,0]]},
thickness=2, linestyle=3):
putletters:=plots[textplot]({[1.75,1.2,
`x`], [1.7,.5,`y`]}, font=[TIMES,BOLD,14]):
circ:=plot([cos(t),sin(t), t=0..Pi/6]):
hd:=plot([[evalf(cos(Pi/6)),evalf(sin(Pi/6))],
[evalf(cos(Pi/6)),evalf(sin(Pi/6)-.2)]],thickness=2):
puttheta:=plots[textplot]([.7,.2,`theta`],
font=[TIMES,BOLD,12]):
plots[display]({puttheta, hd,circ,putletters,slants,base,connectors});