by Fredfredburger » Wed Mar 06, 2013 3:04 am
#39
Given the circumradius of a triangle, denoted by R, and triangle sides a, b, and c, the area can be calculated as
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and rearranging this for R we get
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Here we have an isosceles triangle with congruent sides of length a, and a side of length b.
Given an isosceles we can calculate the area given the two congruent sides and the angle in between those sides
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Plugging this back into the equation we have for the circumradius, we get
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which is your golden formula for these problems. Here since you're finding the diameter you just multiply the radius by 2 and plug and chug.
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MIT '17