Question

What is the length of the diagonal AC in the rectangle below?

Answer 1

Find lengths of BC and DC.

Then use Pythagorean Theorem to find BD (the hypotenuse of right triangle DCB). So Pythag here would be:

$BC^2+DC^2=BD^2$

See attached picture for full work.

Answer 2

I used the distance formula to find the length of diagonal AC.