Question

If the projections of a line on the axes are 9, 12 and 8. Then the length of the line is

• A. 7
• B. 17
• C. 21
• D. 25

Answer 1

The correct option is B 17

Given $rcos\alpha =9,rcos\beta =12$ and $rcos\gamma =8$
$\therefore r^2(co{s}^2\alpha +co{s}^2\beta +co{s}^2\gamma )=81+144+64$
$r^2.1=289$
$r=17$