Question

A circle is inscribed in a triangle with sides $9,12,$ and $15$. The radius of the circle is

Answer 1

The triangle is a perpendicular triangle.

The formulae for finding the radius of circle inscribed is $r=\frac{\Delta }{s}$

where $\Delta =$ Area of triangle

$s=\frac{sumofallthesides}{2}$

$s=\frac{12+15+9}{2}=18$

$\Delta =\frac{1}{2}\times 12\times 9=54$

So, $r=\frac{54}{18}=3$.