The foot of the perpendicular drawn from the point (1, 6, 3) to the line $\frac{x}{1}=\frac{y-1}{2}=\frac{z-2}{3}$ is |
(-1, -1, 1) (1, 2, 3) (1, 3, 5) (1, -3, 5) |
(1, 3, 5) |
The correct answer is Option (3) → (1, 3, 5) The line is $\displaystyle \frac{x}{1}=\frac{y-1}{2}=\frac{z-2}{3}=t$ So any point on the line is: $x=t,\; y=1+2t,\; z=2+3t$ Direction vector: $\langle 1,\,2,\,3\rangle$ Point outside the line: $P(1,6,3)$ Foot of perpendicular = point $Q(t,\;1+2t,\;2+3t)$ such that $\overrightarrow{PQ}$ is perpendicular to the line direction. Compute $\overrightarrow{PQ}$: $\langle t-1,\;1+2t-6,\;2+3t-3\rangle = \langle t-1,\;2t-5,\;3t-1\rangle$ Dot product with direction $\langle 1,2,3\rangle$ must be $0$: $(t-1)\cdot 1 + (2t-5)\cdot 2 + (3t-1)\cdot 3 = 0$ $t-1 + 4t -10 + 9t -3 = 0$ $14t -14 = 0$ $t = 1$ Substitute $t=1$ into line parametric equations: $x = 1$ $y = 1 + 2\cdot 1 = 3$ $z = 2 + 3\cdot 1 = 5$ Foot of perpendicular = $(1,\;3,\;5)$ |