Given the right triangles $ABC$ and $ABD$, what is the length of segment $BC$, in units?
We will use Pythagoras' Theorem to solve for AB.
Actually, we won't even find AB, all we need is AB2.
Then we will use it again to solve for BC.
AB2 = 172 – 72 = 289 – 49 = 240
BC2 = AB2 + AC2 = 240 + 32 = 249
BC = sqrt(249) = 15.78