Can help me solve this problem for topic application of trigonometry

The sides are given of the triangle.
Apply the heron's formula, to find the area of triangle.
[tex]A=\sqrt[]{s(s-a)(s-b)(s-c)}[/tex][tex]s=\frac{21.6+16.4+12.8}{2}=25.4[/tex][tex]A=\sqrt[]{25.4\times3.8\times9\times12.9}=\sqrt[]{11205.972}=105.85sq\mathrm{}cm[/tex]The area of triangle obtained is 105.85 sq.cm.