Draw a line BC = 6 cm. Draw an arc with a radius of 4 cm with the B as center.
Also, draw an arc with a radius of 5 cm taken C as center. Let the bisector of both arcs drawn and they meet at ‘A’. Complete Δ ABC. Let the bisectors of ∠A and∠B be drawn and they meet at ‘O’. Draw an incircle to the triangle with center O.
Radius of the inner circle = r = \(\frac{A}{S}\)
\(r^2=\frac{(s-a)(s-b)(s-c)}{s}\)
\(S=\frac{4+5+6}{2}=\frac{15}{2}=7.5\)
\(r^2=\frac{(7.5-4)(7.5-5)(7.5-6)}{7.5}\)
= \(\frac{3.5\times2.5\times1.5}{7.5}=1.75\)
\(r=\sqrt{1.75}\approx1.3\) cm
