Question

Qual o valor do cos (1050 )? a)(√2+√6)/4 b)(√2-√6)/4 c)(√6-√2)/4 d)(√2-√6)/2 e)(√2-√6)/3​

Answer 1

$\Large\boxed{\begin{array}{l}\sf cos(105^\circ)=cos(60^\circ+45^\circ)\\\sf cos(105^\circ)=cos(60^\circ)\cdot cos(45^\circ)-sen(60^\circ)\cdor sen(45^\circ)\\\sf cos(105^\circ)=\dfrac{1}{2}\cdot\dfrac{\sqrt{2}}{2}-\dfrac{\sqrt{3}}{2}\cdot\dfrac{\sqrt{2}}{2}\\\sf cos(105^\circ)=\dfrac{\sqrt{2}-\sqrt{6}}{4}\end{array}}$