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A circle is inscribed in the equilateral triangle and its radius is 6 cm, what is the area of the equilateral triangle?
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Since the radius of the inscribed circle is r = 6 cm,
the side of the triangle is = 20.785 cm.
Then the area of the triangle is the product of its semi-perimeter and the radius of the inscribed circle
S = = = 187.06 .
See the lessons
Formulas for area of a triangle
Proof of the formula for the area of a triangle via the radius of the inscribed circle
in this site.