The coordinates of the foot perpendicular from the point $(1,0,0)$ to the line $…
- $(2,-3,8)$
- $(1,-1,-10)$
- $(5,-8,-4)$
- $(3,-4,-2)$
Solution

$\therefore \quad L=(2 k+1,-3 \mathrm{k}-1,8 k-10)$. Now, direction ratio of $P L=(2 k,-3 k-1,8$ $-10)$ and direction ratio of $A B=(2,-3,8)$ Since, $P L$ is perpendicular to $A B$ $ \therefore \quad 2(2 k)-3(-3 k-1)+8(8 k-10)=0 $ Now, $k=\frac{2(1-1)+(-3)(0+1)+8(0+10)}{(2)^2+(-3)^2+(8)^2}$ $ =\frac{0-3+80}{4+9+64}=\frac{77}{77}=1 $ $\therefore \quad$ Required co-ordinate $ =L=(2+1,-3-1,8-10)=(3,-4,-2) \text {. } $
Asked in: JEE Main 2012 (12 May Online)