Question

a partir dos angulos notaveis calcule: sen 255º

Answer 1

-0,96  fiz na calculadora

Answer 2

$sin(255)=-sin(75)$

$sin(75)=sin(45+30)=sin(45)cos(30)+sin(30)cos(45)$
$\frac{\sqrt2}{2}\times\frac{\sqrt3}{2}+\frac12\times\frac{\sqrt2}{2}=\frac{\sqrt6}{4}+\frac{\sqrt2}{4}$
$-sin(75)=\boxed{\frac{-\sqrt6-\sqrt2}{4}}$