Here is the question:
In a triangle ABC, AB=AC, and angle A is equal to 36 degrees. Point D is on AC so that BD bisects angle ABC.
(a) Prove that BC=BD=AD
(b) Let x = BC and let y = CD. Using similar triangles BCD and ABC, write an equation involving x and y.
(c) Let r=u/x. Write the equation from Part (b) in terms of and find
(d) Find cos 36 and cos 72 using Parts a-c. (Do not use your calculator!)