Come l'insegnante puņ costruire figure come questa con R (vedi):

source("http://macosa.dima.unige.it/r.R")
# Ricordiamo che invece di "black" abbiamo usato il numero 1
# La figura "soluzione", ideata per preparare l'esercizio
BF=5; HF=2.8
PLANE(0,24, 0,12)
coldash=1
gridH(0:12); gridV(0:24)
circle(4,11,1, 1)
segm(4,10, 4,6, 1)
segm(4,6, 2,0, 1)
segm(4,6, 6,0, 1)
segm(4,9, 0,7, 1)
segm(4,9, 8,7, 1)
circle(13,5.5,1/2, "blue")
segm(13,5, 13,3, "blue")
segm(13,3, 12,0, "blue")
segm(13,3, 14,0, "blue")
segm(13,4.5, 11,3.5, "blue")
segm(13,4.5, 15,3.5, "blue")
circle(21,11*3/4,3/4, "brown")
segm(21,10*3/4, 21,6*3/4, "brown")
segm(21,6*3/4, 21-2*3/4,0, "brown")
segm(21,6*3/4, 21+2*3/4,0, "brown")
segm(21,9*3/4, 21-4*3/4,7*3/4, "brown")
segm(21,9*3/4, 21+4*3/4,7*3/4, "brown")
##
# La figura senza l'indicazione delle coordinate e senza alcuni pezzi
PLANEww(0,24, 0,12)
coldash=1
gridH(0:12); gridV(0:24)
circle(4,11,1, 1)
segm(4,10, 4,6, 1)
# segm(4,6, 2,0, 1)
# segm(4,6, 6,0, 1)
segm(4,9, 0,7, 1)
segm(4,9, 8,7, 1)
# circle(13,5.5,1/2, "blue")
segm(13,5, 13,3, "blue")
segm(13,3, 12,0, "blue")
segm(13,3, 14,0, "blue")
segm(13,4.5, 11,3.5, "blue")
segm(13,4.5, 15,3.5, "blue")
circle(21,11*3/4,3/4, "brown")
segm(21,10*3/4, 21,6*3/4, "brown")
# segm(21,6*3/4, 21-2*3/4,0, "brown")
segm(21,6*3/4, 21+2*3/4,0, "brown")
segm(21,9*3/4, 21-4*3/4,7*3/4, "brown")
segm(21,9*3/4, 21+4*3/4,7*3/4, "brown")