Equilateral triangle

Calculate the area of an equilateral triangle with circumference 72cm.

Correct answer:

S =  249.4153 cm²

Step-by-step explanation:

$$\begin{gathered} o=72\text{ cm } \\ a=o\mathrm{/}3=72\mathrm{/}3=24\text{ cm } \\ S=ah\mathrm{/}2 \\ h=\sqrt{3}\mathrm{/}2a \\ S=a^2\cdot \sqrt{3}\mathrm{/}4=24^2\cdot \sqrt{3}\mathrm{/}4=144\sqrt{3}=249.4153{\text{cm}}^2 \end{gathered}$$

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