Question

se o cos de alfa=2/3 determine X

Answer 1

     $\cos \alpha=\dfrac{\textsf{cateto adjacente ao \^angulo }\alpha}{\textsf{hipotenusa}}\\\\\\ \cos \alpha=\dfrac{8}{x}=\dfrac{2}{3}\\\\\\ 2x=3\cdot 8\\\\ 2x=24\\\\ x=\dfrac{24}{2}$

     $x=12~\mathrm{cm}\quad\longleftarrow\quad\textsf{resposta.}$


Bons estudos! :-)