Question

Encontre o cosseno da medida do ângulo entre os planos 2x - y - 2z- 5 = 0 e 6x - 2y + 3z + 8 = 0

Answer 1

$\cos \theta =\dfrac{(2,-1,-2)\cdot(6,-2,3)}{\|(2,-1,-2)\|\cdot\|(6,-2,3)\|} \\ \\ \\ \cos \theta =\dfrac{12+2-6}{\sqrt{4+1+4}\cdot\sqrt{36+4+9}}\\ \\ \\ \cos \theta =\dfrac{8}{3\cdot 7}\\ \\ \\ \boxed{\cos \theta =\dfrac{8}{21}}$