Consider the triangle OBC,
As all the three sides of the given triangle is known. consider the traingle ODC the right triangle.
[tex]\begin{gathered} \frac{BC}{2}=\frac{8.7}{2}=4.35 \\ it\text{ implies DC=4.35} \\ \end{gathered}[/tex]
The height is given as,
[tex]\begin{gathered} As\text{ ODC is right triangle, using the pythagorean theorem,} \\ OC^2=OD^2+DC^2 \\ 10^2=OD^2+4.35^2 \\ OD^2=81.0775 \\ OD=9 \end{gathered}[/tex]
The area of triangle OBC is,
[tex]\begin{gathered} A=\frac{1}{2}\times b\times h \\ A=\frac{1}{2}\times8.7\times9 \\ A=39.15 \end{gathered}[/tex]
