# Find the d . c. s of a vector whose direction ratios are $2 , 3 , -6.$

Toolbox:
• The d.c.s of a vector with d.r.s $(a,b,c)$ are $\large\frac{a}{\sqrt{a^2+b^2+c^2}}, \large\frac{b}{\sqrt{a^2+b^2+c^2}}, \large\frac{c}{\sqrt{a^2+b^2+c^2}}$
The d.c.s of vector with d.r.s $(2,3,-6)$ are $\large\frac{2}{\sqrt{4+9+36}},\large\frac{3}{\sqrt{4+9+36}},\large\frac{-6}{\sqrt{4+9+36}} = \large\frac{2}{7},\large\frac{3}{7},\large\frac{-6}{7}$