There are two ways to find the radius of circumscribing circle of a triangle (triangle inside the circle and whose three vertices are on the circle).
Choose one that you can easily remember:Method A:
1.) Find the semi-perimeter (s) of the triangle, where a, b, and c are the sides
of the triangle:
s = (a + b+ c) ÷ 2
2.) Solve for the radius (r) given the semi-perimeter (s) of the triangle, and the
the sides a, b, and c:
r = Solution using Method A:
a = 80 cm; b = 100 cm; c = 140 cmFind the triangle's semi-perimeter
: (half of the triangle's perimeter)
s = (80 + 100 + 140) ÷ 2
s = 320 cm ÷ 2
s = 160 cmSolve for radius given the semi-perimeter (160 cm) and sides a, b, c:
r = (abc) ÷
r = r ≈ 71.44 cm ANSWER: The radius of circumscribing circle is 71.44 cm.
Substitute the given measurements of sides a, b and, c, then evaluate.
The result is the same.