[Math] Find the length of the sides in an Isosceles triangle, given its area and perimeter

triangles

How can I determine the length of the sides $b$, and the altitude $h$ of an isosceles triangle given its area $A= 24 \text{cm}^2$ and its perimeter $P= 16\text{cm}$?

Best Answer

Let $a$ be the length of one side and let $b$ be the length of the other two sides, and let $h$ be the altitude.

By Pythagorean Theorem we have that $$\left(\frac{1}{2}a\right)^2 + h^2 = b^2$$

We also have that $a + 2b = 16$ and $\dfrac{1}{2}ah = 24$.

Solve this system of $3$ equations.

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