If P (2, 3, –6) and Q (3, –4, 5) are two points, the direction cosines of line PQ are

$\frac{1}{\sqrt{171}},-\frac{7}{\sqrt{171}}, \frac{11}{\sqrt{171}}$

P ≡ (2, 3, − 6), Q ≡ (3, − 4, 5)

direction ratios = <1, − 7, 11>

direction cosines = $\left(\frac{1}{\sqrt{1+49+121}}, \frac{-7}{\sqrt{1+49+121}}, \frac{11}{\sqrt{1+49+121}}\right)$

$=\left(\frac{1}{\sqrt{171}}, \frac{-7}{\sqrt{171}}, \frac{11}{\sqrt{171}}\right)$