Question

Calcular o valor da expressão a seguir:

Answer 1

Resposta:

Alternativa E

Explicação passo-a-passo:

$x = \cos( \frac{\pi}{4} ) \times \cos( \frac{\pi}{2} ) + \cos( \pi ) \times \cos( \frac{\pi}{6} )$

$\cos( \frac{\pi}{4} ) = \frac{ \sqrt{2} }{ 2 } \\ \\ \cos( \frac{\pi}{2} ) = 0 \\ \\ \cos(\pi) = - 1 \\ \\ \cos( \frac{\pi}{6} ) = \frac{ \sqrt{3} }{2}$

$x = \frac{ \sqrt{2} }{2} \times 0 + ( - 1) \times \frac{ \sqrt{3} }{2} \\ \\ x = - \frac{ \sqrt{3} }{2}$

Answer 2

Resposta:

$\textsf{Leia abaixo}$

Explicação passo a passo:

$\mathsf{x = \dfrac{\pi }{4}\:.\:cos\:\dfrac{\pi }{2} + cos\:\pi\:.\:cos\:\dfrac{\pi }{6}}$

$\mathsf{x = cos\:45\textdegree\:.\:cos\:90\textdegree + cos\:180\textdegree\:.\:cos\:30\textdegree}$

$\mathsf{x = \dfrac{\sqrt{2}}{2}\:.0 + (-1)\:.\:\dfrac{\sqrt{3}}{2}}$

$\boxed{\boxed{\mathsf{x = -\dfrac{\sqrt{3}}{2}}}}\leftarrow\textsf{letra E}$