# 11.8.4. Heron's Formula

Determine to the nearest 3 decimal places the area of an isosceles triangle whose side length is

- A
- B
- C
- D

### Example

Determine to the nearest 3 decimal places the area of an isosceles triangle whose side length is

### Solution

The isosceles triangle is composed of two right-angled triangles. Each has interior angles measuring

Now use the sine rule to find the approximate length,

According to Heron's formula, the area of a triangle whose side lengths are

Thus, the approximate area of the isosceles triangle is