Is a triangle with sides of lengths 24, 70 and 74 a right triangle?

1 Answer
Nov 14, 2015

Yes

Explanation:

24^2+70^2=576+4900=5476=74^2

So these side lengths satisfy Pythagoras Theorem.

An alternative way of approaching this might be as follows:

24, 70 and 74 are all divisible by 2, so this triangle is a right angled triangle if and only if a triangle with sides 12, 35 and 37 is a right angled triangle.

Notice that 35 = 6^2-1, 37 = 6^2+1 and 12 = 2*6. This looks like a pattern we could check:

(a^2-1)^2 = a^4-2a^2+1

(a^2+1)^2 = a^4+2a^2+1

(2a)^2 = 4a^2

So:

(a^2+1)^2 = a^4+2a^2+1 = a^4-2a^2+1+4a^2 = (a^2-1)^2+(2a)^2

In our case a=6, but any number a would work.