In a right triangle BAC (see figure)
cevians BD and CE meet at F so that the measure
of angles ACE, ADE, and BCE are 10, 20, and 30 degrees, respectively.
Find the measure of angle BFE.
Try to you use elementary geometry (Euclid's Elements).
See also:
Geometric variations of problem 964.
Typography Art of Problem 964 using Mobile Apps, iPad
