Question

the radius of the incircle of a triangle whose sides are 9cm, 12cm, and 15cm is​

Answer 1

$\red{\boxed{Answer}}$

The inradius r of the incircle in a triangle with sides of length a, b, c is given by

r = $\sqrt{ \frac{(s* (s -a)*(s-b)*(s-c)) }{s} }$

where s = $\frac{(a + b + c)}{2}$

Here a = 9, b = 12 and c = 15

So s = $\frac{36}{2}$ = 18

r = sqrt of $\frac{(18 \times 9 \times 6 \times 3)}{18}$

= $\frac{54}{18}$

$\implies{\red{\boxed{3}}}$