If the radius of the circumcircle of an equilateral triangle is 8 cm, then the measure of radius of its incircle is:
As per the given question,
We know that circumradius of an equilateral triangle $$(R)=\dfrac{a}{\sqrt{3}}$$
And radius of incircle $$(r) =\dfrac{a}{2\sqrt{3}}$$
Hence,
$$\dfrac{R}{r}=\dfrac{\dfrac{a}{\sqrt{3}}}{\dfrac{a}{2\sqrt{3}}}$$
$$\Rightarrow \dfrac{R}{r}=2$$
$$\Rightarrow r=\dfrac{R}{2}=\dfrac{8}{2}=4$$cm
$$\Rightarrow r=4cm$$
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