The distance of a point \( P(a, b, c) \) from the y-axis is the perpendicular distance from \( P \) to the y-axis.
The y-axis corresponds to the line where \( x = 0 \) and \( z = 0 \).
The perpendicular distance is: \[ \text{Distance} = \sqrt{(a - 0)^2 + (c - 0)^2} = \sqrt{a^2 + c^2}. \]
Therefore, the correct answer is (C) \( \sqrt{a^2 + c^2} \).
Consider the line \[ \vec{r} = (\hat{i} - 2\hat{j} + 4\hat{k}) + \lambda(-\hat{i} + 2\hat{j} - 4\hat{k}) \]
Match List-I with List-II:
| List-I | List-II |
|---|---|
| (A) A point on the given line | (I) \(\left(-\tfrac{1}{\sqrt{21}}, \tfrac{2}{\sqrt{21}}, -\tfrac{4}{\sqrt{21}}\right)\) |
| (B) Direction ratios of the line | (II) (4, -2, -2) |
| (C) Direction cosines of the line | (III) (1, -2, 4) |
| (D) Direction ratios of a line perpendicular to given line | (IV) (-1, 2, -4) |

A ladder of fixed length \( h \) is to be placed along the wall such that it is free to move along the height of the wall.
Based upon the above information, answer the following questions:
(iii) (b) If the foot of the ladder, whose length is 5 m, is being pulled towards the wall such that the rate of decrease of distance \( y \) is \( 2 \, \text{m/s} \), then at what rate is the height on the wall \( x \) increasing when the foot of the ladder is 3 m away from the wall?