Hi everyone! I am new to this website and I need a bit of help with this problem. I do not need you to answer the problem for me, just walk me through a few steps/hints and I will try to solve it on my own.
In triangle ABC, AB = AC, and angle A is equal to 36 degrees. Point D is on line AC so that line 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 = \frac{y}{x}. Write the equation from Part (b) in terms of r, and find r.
(d) Find cos(36) and cos(72) using Parts a-c.
This is a problem from the Introduction to Geometry course at Art of Problem Solving.
I have currently solved parts (a) through (c).
