Question

se sen x = -12\13, com x no 3 quadrante, determine

Answer 1

$\boxed{\begin{array}{l}\sf sen(x)=-\dfrac{12}{13}\longrightarrow sen^2(x)=\dfrac{144}{169}\\\\\sf cos^2(x)=\dfrac{169}{169}-\dfrac{144}{169}=\dfrac{25}{169}\\\\\sf cos(x)=-\sqrt{\dfrac{25}{169}}\\\\\boxed{\boxed{\boxed{\boxed{\sf\red{\maltese}~\blue{ cos(x)=-\dfrac{5}{13}} }}}}\end{array}}$