[tex]\bf \textit{using the pythagorean theorem} \\\\ c^2=a^2+b^2\implies \sqrt{c^2-a^2}=b \qquad \begin{cases} c=\stackrel{hypotenuse}{10}\\ a=\stackrel{adjacent}{9.7}\\ b=opposite\\ \end{cases} \\\\\\ \sqrt{10^2-9.7^2}=b\implies \sqrt{5.91}=b\implies 2.43\approx b \\\\[-0.35em] ~\dotfill\\\\ \stackrel{\textit{perimeter}}{10+9.7+2.43}\implies 22.13[/tex]
