Sezione 4.   Esempi

% Circonferenza inscritta e bisettrici
A B C triangle
draw(A, B, C)
draw(incircle(A, B, C))
draw(bisector(B, A, C), dotted)
draw(bisector(A, B, C), dotted)
draw(bisector(B, C, A), dotted)

% Circolo di Feuerbach
A B C triangle
a = projection(A, line(B, C))
b = projection(B, line(A, C))
c = projection(C, line(A, B))
draw(A, B, C)
draw(a) ; draw(b) ; draw(c)
draw(segment(A, a), dotted)
draw(segment(B, b), dotted)
draw(segment(C, c), dotted)
draw(barycenter(A, B))
draw(barycenter(B, C))
draw(barycenter(C, A))
draw(circle(a, b, c))

% Triangolo isoscele
A B C isosceles
H = projection(C, line(A, B))
draw(A, B, C)
draw(H)
draw(segment(C, H), dashed)
mark(B, H, C, right)
mark(segment(A, H))
mark(segment(B, H))
mark(segment(A, C), cross)
mark(segment(C, B), cross)
mark(B, A, C, double)
mark(C, B, A, double)

% Punti allineati
A B C D square
A B E equilateral(4)
B F G equilateral(4, 30:)
draw(A, B, C, D)
draw(A, B, E)
draw(B, F, G)
draw(line(E, F), dotted)

% Angoli di un parallelogrammo
A B C D parallelogram(5, 4, 105:)
draw(A, B, C, D)
mark(B, A, D)
mark(D, C, B)
mark(C, B, A, double)
mark(A, D, C, double)

% Somma vettoriale
A B C D parallelogram
draw(segment(A, B), full, arrow)
draw(segment(A, C), full, arrow)
draw(segment(A, D), full, arrow)
draw(segment(B, C), dotted)
draw(segment(D, C), dotted)

% Tangenti a una circonferenza
O = point(2, 2)
C = circle(O, 2)
A = point(6.5, 2)
c = circle(O, A)
I J intersection(C, c)
color(lightgray)
draw(line(A, I))
draw(line(A, J))
color(black)
draw(O, plus)
draw(A)
draw(C)
draw(c, dotted)

% Una spirale
frame(-5, -4, 5, 4)
trace(t, 0, 3*360)
{ point(t/360, t:) }

% Parabola con fuoco e direttrice
F = point(3, 1.5)
D = line(point(1, 0.5), -65:)
C = parabola(F, D)
draw(F)
draw(D)
draw(C)