Rect[x_,y_,L_,α_]:=Polygon[{{x,y},{x+L Cos[α],y+L Sin[α]},{x+L Cos[α]-L Sin[α],y+L Sin[α]+L Cos[α]},{x-L Sin[α],y+L Cos[α]},{x,y}}]
Boom[x_,y_,L_/;L>2,α_]:=Module[{sa,ca,sa1,ca1,a,b,c},sa=Sin[α];ca=Cos[α];
sa1=Sin[α+π/4];ca1=Cos[α+π/4];
a=Boom[x-L*sa,y+L*ca,L/Sqrt[2],α+π/4];
b=Boom[x-L*sa+L/Sqrt[2]*ca1,y+L*ca+L/Sqrt[2]*sa1,L/Sqrt[2],α-π/4];
c=Rect[x,y,L,α];
{a,b,c}]
Boom[x_,y_,L_/;L≤2,α_]:=Module[{},Rect[x,y,L,α]]
Graphics[Boom[0,0,10,0]]

onderzoek mbv Manipulate hoe de boom verandert met L tussen 2 en 40