Cho hai mặt phẳng (P): ax +by+ cz +d =0; (Q): a'x +b'y+ c'z+d'=0. Công thức tính cô

A.$\cos \left(\left(P\right),\left(Q\right)\right)=\frac{\left|a.a^{\text{'}}+b.b^{\text{'}}+c.c^{\text{'}}\right|}{\sqrt{a^2+b^2+c^2}.\sqrt{a^{\text{'}2}+b^{\text{'}2}+c^{\text{'}2}}}$

B.$\cos \left(\left(P\right),\left(Q\right)\right)=\frac{a.a^{\text{'}}+b.b^{\text{'}}+c.c^{\text{'}}}{\sqrt{a^2+b^2+c^2}.\sqrt{a^{\text{'}2}+b^{\text{'}2}+c^{\text{'}2}}}$

C. $\cos \left(\left(P\right),\left(Q\right)\right)=\frac{a.a^{\text{'}}+b.b^{\text{'}}+c.c^{\text{'}}}{\sqrt{a+b+c}.\sqrt{a^{\text{'}}+b^{\text{'}}+c^{\text{'}}}}$

D. $\cos \left(\left(P\right),\left(Q\right)\right)=\frac{\left|a.a^{\text{'}}+b.b^{\text{'}}+c.c^{\text{'}}\right|}{{\sqrt{a+b+c}}^2.{\sqrt{a^{\text{'}}+b^{\text{'}}+c^{\text{'}}}}^2}$