Which pair of triangles must be similar?
Triangle 5 has a 30∘ angle and a 90∘ angle. Triangle 6 has a 30∘ angle and a 70∘ angle.
Triangles 1 and 2 each have a 35∘ angle.
Triangle 7 has a 50∘ angle and a 25∘ angle. Triangle 8 has a 50∘ angle and a 105∘ angle.
Triangles 3 and 4 are both isosceles. They each have a 40∘ angle.