Question 1210260
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Find the area of the triangle with side lengths 4, 5, and 8.
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Use the Heron's formula.


<U>ANSWER</U>.  The area of the triangle is 8.1815 square units, approximately.



I used the online calculator 

https://www.omnicalculator.com/math/herons-formula


one of many possible online calculators of this kind.



The referred calculator/web-site  has all necessary descriptions and explanations
to the formula, and even a proof of it.