下图显示了一个等腰三角形 XYZ，其中 XY = YZ。 WY = 12 cm，YZ = 15 cm 且 XZ = 18 cm。求三角形 WXY 的面积。

1. Find the length of the base XW of triangle WXY

Since triangle XYZ is an isosceles triangle with $XY = YZ$, the perpendicular line WY from Y to the base XZ bisects the base.
$XW = 18 \div 2 = 9\text{ cm}$

2. Calculate the area of triangle WXY

$\text{Area of } \triangle WXY = \frac{1}{2} \times \text{base} \times \text{height}$
$\text{Area} = \frac{1}{2} \times 9 \times 12 = 54\text{ cm}^2$