**The diagonals of an isosceles trapezoid have the same length.**

This theorem also holds true in reverse, meaning, we can determine that a certain trapezoid is isosceles if we know that its diagonals are equal.

You can use this theorem in the exam as you see it and you will not need to prove it.

**The second property:**

**Given the isosceles trapezoid** **$ABCD$**** it holds that:**

$⊿ADC=⊿BCD$

**Observe-** You will need to prove this property in the exam. We can prove it based on the SSS congruence theorem.