Question

Find the area of a triangle whose sides are $16$ cm, $19$ cm, and $21$ cm in length.

Answer 1

$s=\frac{a+b+c}{2}\Rightarrow s=\frac{16+19+21}{2}\Rightarrow s=28$

$A=\sqrt{s(s-a)(s-b)(s-c)}$

$=\sqrt{28(28-16)(28-19)(28-21)}$

$=\sqrt{28\left(12\right)\left(9\right)\left(7\right)}$

$=\sqrt{21168}$

$=145.49$ sq cm