If two triangles have two internal angles which are common, the third angle must be common, since the sum of the intermal angles is 180°. If two triangles of different dimensions are similar, the corresponding sides are proportional to each other- Exercises If α-200 what is the angle ofy? 2. If α 200 what is the p? What is γ? 3. 5 ft What is the length of side a for the right triangle? 3 ft