Online Geometry Problem 40: Triangle, Incenter, Excenter, 40, 60, 80 Degrees. High School, College, Mathematics Education

In
triangle ABC, the
angles
A and B measure 80 and 40 respectively, I
is the
incenter and E the
excenter. AB and CE meet at D. If BC = a, AC = b and CI = d,
prove
that
.