
Re: Three halfcircles
Posted:
Sep 4, 2011 12:45 PM


> Let DEF be a rectangular triangle such that D=[0 0 > 0], E=[3 0 0] and F=[0 4 0]. On the sides DE, DF and > EF are constructed respective halfcircles with > positive zaxis and perpendicular to the xyplane. > Determine the parameters A, B, C of the plane A*x + > B*y + C*z = 1 , that tangents the three > halfcircles.
Hello Avni, thanks for this interesting puzzle. I obtained A = 3/16, B = 4/9, C = 5/6. I did not attempt for a "clever" solution; I just wrote down the parametric equations of the three circles, then wrote down the conditions of their tangency to the plane, and solved the resulting system of six equations in six unknowns.
Rouben

