Consider the line $\frac{x-2}{2}=\frac{2y-5}{-3},z=-1$. Then which of the following is/are true? (A) It has Direction ratios (2, -3, -1) Choose the correct answer from the options given below: |
(A) only (A) and (B) only (C) and (D) only (A) and (C) only |
(C) and (D) only |
The correct answer is Option (3) → (C) and (D) only Given line: $\frac{x - 2}{2} = \frac{2y - 5}{-3},\ z = -1$ Rewrite the second equation: $\frac{2y - 5}{-3} \Rightarrow \frac{y - \frac{5}{2}}{-\frac{3}{2}}$ Thus, the symmetric form is: $\frac{x - 2}{2} = \frac{y - \frac{5}{2}}{-\frac{3}{2}},\ z = -1$ This is a line parallel to the vector: Direction ratios = $(2,\ -\frac{3}{2},\ 0)$ Hence, (C) is correct. Now compute direction cosines: Let $\vec{v} = \langle 2,\ -\frac{3}{2},\ 0 \rangle$ $|\vec{v}| = \sqrt{2^2 + \left(-\frac{3}{2}\right)^2 + 0^2} = \sqrt{4 + \frac{9}{4}} = \sqrt{\frac{25}{4}} = \frac{5}{2}$ Direction cosines: $\left( \frac{2}{\frac{5}{2}},\ \frac{-\frac{3}{2}}{\frac{5}{2}},\ 0 \right) = \left( \frac{4}{5},\ -\frac{3}{5},\ 0 \right)$ Hence, (D) is correct. |