Recordemos las razones trigonométricas(ver imagen), entonces nos piden
[tex]\begin{array}{c}\sf{25\times \sin^2(\alpha)}\\\\\sf{25\times\left(\dfrac{4}{5}\right)^2}\\\\\sf{25\times\dfrac{16}{25}}\\\\\sf{\not \!\!25\times\dfrac{16}{\not \!\!25}}\\\\\boxed{\boxed{\boldsymbol{\red{\sf{16}}}}}\\\end{array}[/tex]
[tex]\boxed{\sf{{R}}\quad\raisebox{10pt}{$\sf{\red{O}}$}\!\!\!\!\raisebox{-10pt}{$\sf{\red{O}}$}\quad\raisebox{15pt}{$\sf{{G}}$}\!\!\!\!\raisebox{-15pt}{$\sf{{G}}$}\quad\raisebox{15pt}{$\sf{\red{H}}$}\!\!\!\!\raisebox{-15pt}{$\sf{\red{H}}$}\quad\raisebox{10pt}{$\sf{{E}}$}\!\!\!\!\raisebox{-10pt}{$\sf{{E}}$}\quad\sf{\red{R}}}\hspace{-64.5pt}\rule{10pt}{.2ex}\:\rule{3pt}{1ex}\rule{3pt}{1.5ex}\rule{3pt}{2ex}\rule{3pt}{1.5ex}\rule{3pt}{1ex}\:\rule{10pt}{.2ex}[/tex]
