Question

Part 3 thanks you :D

Answer 1

The converse of the Pythagorean Theorem:
If c^2 = a^2 + b^2 then the triangle is a right triangle

c = longest side, a and b are the other two sides

c = 65, a = 16 and b = 63

So

c^2 = 65^2 = 4225
a^2 + b^2 = 16^2 + 63^2 = 256 + 3969 = 4225

In this case
c^2  = a^2 + b^2
4225 = 4225

Triangle ABC is a right triangle