Question

In the relation between direction ratios and direction cosines, what does the sign \[\pm\] in \[l=\pm\frac{a}{\sqrt{a^2+b^2+c^2}}\] depend on?

Options

• The distance between two points

• The positive x-axis only

• The chosen direction of the line

• The value of \[a^2+b^2+c^2\] only

Answer 1

A line can be given either of two opposite directions. The sign \[\pm\] depends on which direction of the line has been chosen.