Answer:
Triangle 3: 3, 4 ,5
Step-by-step explanation:
Well, you can easily tell by 3, 4, 5 being a Pythagorean triple.
But you have to use the Pythagorean Theorem to solve this.
So you get the side lengths of the two shortest sides, and you add the squared versions of them together.
So: 3^2+4^2 and if that equals the biggest side:5^2 then it's a right triangle.
