What is the length of a diagonal of a square with a side length of 6?
A) 3 B)\sqrt{3} C)3\sqrt{2} D)6\sqrt{2}

Use pythagorean’s theorem and find the missing side lengths of the two smaller triangles and add them together
13^2 - 12^2 = 5
15^2 - 12^2 = 9
5+9 = 14
14 is the length of each side of the square
14^2 + 14^2 = 19.8
19.8 is the diagonal length of the inside if the square