Explain why a square can never be a trapezoid

isaiah walks 3 miles due north, turns and then 5 miles due east. how far is he from his starting point?

a^2 + b^2 = c^2

let c = distance from starting point.

(3)^2 + (5)^2 = c^2

9 + 25 = c^2

34 = c^2

sqrt{34} = sqrt{c^2}

sqrt{34} = c

cross multiplying, we get :

⇒ (3) × (5) = (9) × (x)

⇒ 15 = 9x