What is the radius of the circular mold? 5.34 cm 9.62 cm 11.35 cm 18 cm

I saw the image of the triangle. It will be a circle inscribed in an isosceles triangle.
sides a and b have 18 cm and side c have 20 cm.
The triangle can be divided into 2 right triangles with 10 cm base, 18 cm hypotenuse. We need to find the measure of the long side to get the height of the isosceles triangle.
a² + b² = c² a² + (10cm)² = (18cm)² a² = 324 cm² - 100 cm²a² = 224 cm²a = √224 cm²a = 14.97 cm
Area = 1/2 * base * heightA = 1/2 * 20 cm * 14.97 cmA = 149.70 cm²
A = r/2 * p149.70 cm² = r/2 * (18cm+18cm+20cm)149.70 cm² = r/2 * 56 cm149.70 cm² ÷ 56 cm = r/22.67 cm = r/22.67 cm * 2 = r5.34 cm = r
Radius is 5.35 cm.
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