G-4 Cyclic Equilateral

Geometry Level 3

An equilateral triangle is inscribed in a circle with an area equal to 150 π 150\pi square units. If the area of the triangle can be expressed as a b c \frac{a \sqrt{b}}{c} square units in simplified and lowest term. Find a + b + c a+b+c .


The answer is 230.

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1 solution

Brian Dela Torre
Jan 29, 2016

Obtain first the radius of the from the given area of the circle. This gives the value of the radius,

r = 150 Π Π \sqrt{\frac{150Π}{Π}} = 5 6 \sqrt{6} units.

Since the triangle is inscribed in a circle, then r= s 3 \frac{s}{\sqrt{3}}

5 6 \sqrt{6} = s 3 \frac{s}{\sqrt{3}} or s = 15 2 \sqrt{2} units,

Hence the area of the triangle is,

A = ( 15 2 ) 2 4 \frac{(15\sqrt{2})^{2}}{4} = 225 3 2 \frac{225\sqrt{3}}{2} = a b c \frac{a\sqrt{b}}{c}

The sum of a+b+c = 225+ 3 + 2 = 230 \boxed{230}

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