A line passes through the points (6, - 7, -1) and (2,-3,1). If the angle $\alpha$  which the line makes with the positive direction of x-axis is acute, the direction cosines of the line are 

$\text{ The direction cosines of the given line are proportional to }$$2-6,-3+7,1+1\text{, i.e., }-2,2,1\text{. Therefore, direction cosines }$

$\text{ are }\frac{\mp 2}{3},\frac{\pm 2}{3},\frac{\pm 1}{3}$

$\text{ Since the angle }\alpha \text{ which the line makes with positive direction }$$\text{ of }x\text{-axis is acute, }\cos \alpha >0\Rightarrow \cos \alpha =2/3\text{, Thus, required }$

$\text{ direction cosines are }2/3,-2/3,-1/3$