# 8.4.4. Corollaries of Isosceles Triangle Theorems

In the figure below,

- A
- B
- C
- D

### Example

In the figure below,

### Solution

Step 1: Find the length of

Use Pythagoras' theorem, which states that the square of the
length of a right-angled triangle's hypotenuse is equal to the sum
of the squares of the lengths of the other two sides.

Step 2: Find the length of

If the hypotenuse and one other side of a right-angled triangle are congruent to the corresponding parts of another right-angled triangle, then the two triangles are congruent.

Since

Therefore,

Step 3: Find the area of