Let ABC be a triangle with AB = AC and ∠BAC = 20°, and let P be a point on side AB such that AP = BC. Find ∠ACP. I know that ABC is a isosceles triangle with B and C as 80° each. Since two segments are equal to each other, there is probably something involving either congruent or similar triangles, or both.  Can I get a hint for how to solve this? Thank you.