Question

If the projections of a line on the co-ordinate axes be $2,-1,2$, then the length of the lines is

• A. $3$
• B. $4$
• C. $2$
• D. $\frac{1}{2}$

Answer 1

Answer: (A)

$3$

let $l,m$ and $n$ be the projection of a line on the co-ordinate axes .since,

since,$l=2,m=-1,n=2$

length of the line$=\sqrt{l^2+m^2+n^2}$

$=\sqrt{2^2+(-1{)}^2+2^2}$

$=3$

Hence, Option A is correct.