Question

The direction cosines of the normal to the plane 2x + 3y - 6z = 5 are

• A. $(2,3,-6)$
• B. $\frac{2}{7},\frac{3}{7},-\frac{6}{7}$
• C. $\frac{2}{5},\frac{3}{5},-\frac{6}{5}$
• D. None of these

Answer 1

The correct option is B $\frac{2}{7},\frac{3}{7},-\frac{6}{7}$

Direction ratios of normal to the plane are (2,3,-6)
$\therefore$ Direction cosines are $(\frac{2}{\sqrt{49}},\frac{3}{\sqrt{49}},-\frac{6}{\sqrt{49}})$ or $(\frac{2}{7},\frac{3}{7},\frac{-6}{7})$.