题目
直线 L_1: (x-2)/(1) = (y-1)/(-2) = (z-3)/(2) 与 L_2: (x)/(2) = (y-1)/(1) = (z+1)/(-3) 的夹角余弦为 ____。A. -(2)/(sqrt(14))B. (2)/(sqrt(14))C. (1)/(sqrt(7))D. -(1)/(sqrt(7))
直线 $L_1: \frac{x-2}{1} = \frac{y-1}{-2} = \frac{z-3}{2}$ 与 $L_2: \frac{x}{2} = \frac{y-1}{1} = \frac{z+1}{-3}$ 的夹角余弦为 ____。
A. $-\frac{2}{\sqrt{14}}$
B. $\frac{2}{\sqrt{14}}$
C. $\frac{1}{\sqrt{7}}$
D. $-\frac{1}{\sqrt{7}}$
题目解答
答案
B. $\frac{2}{\sqrt{14}}$