A nice geometry exercise!

[@zdrastvutye]

it all ends up with interpolation in a squared 2nd degree equation:
10 print "geosolve-a nice geometry exercise":dim x(2,2),y(2,2)
20 l1=1:w1=100:w2=20:xa=0:ya=l1*sin(rad(w1)):xb=l1*abs(cos(rad(w1))):yb=0
30 lbc=sin(rad(180-w1-w2))/sin(rad(w2))*l1:xc=xb+lbc:yc=0
40 lac=l1*sin(rad(w1))/sin(rad(w2)):dx=(xc-xa)*l1/lac:xe=xa+dx
50 dy=(yc-ya)*l1/lac:ye=ya+dy:disx=l1^2-ye^2:if disx

[@GeoSolve]

Thanks for sharing.