JEE Main 20246 AprilMorning Shift
- Exam
- JEE Main
- Year
- 2024
- Date
- 6 April
- Shift
- Morning Shift
- Subject
- Mathematics
- Chapter
- Three Dimensional Geometry
JEE Main 2024 · 6 April · Morning Shift · Mathematics · Three Dimensional Geometry
The shortest distance between the lines...
The shortest distance between the lines and is
Options
- A
- B
- C
- D
Correct answer
B.
Step-by-step solution
\begin{aligned} & \frac{x-3}{2}=\frac{y+15}{-7}=\frac{z-9}{5} & \frac{x+1}{2}=\frac{y-1}{1}=\frac{z-9}{-3} \\ & \text{ S.D }=\frac{\left|\left(\overline{\mathrm{a}_2 \cdot \overline{\mathrm{a}_1\right) \cdot\left(\overline{\mathrm{b}_1 \cdot \overline{\mathrm{b}_2\right)\right|}{\left|\overline{\mathrm{b}_1 \times \overline{\mathrm{b}_2\right|} \\ & a_1=3,-15,9 \\ & \mathrm{ b}_1=2,-7,5 \\ & \mathrm{a}_2=-1,1,9 \\ & \mathrm{ b}_2=2,1,-3 \\ & a_2-a_1=-4,16,0 \\ & \overline{\mathrm{b}_1 \times \overline{\mathrm{b}_2=\left|\begin{array}{ccc}\hat{\mathrm{i}} & \hat{\mathrm{j}} & \hat{\mathrm{k}} \\ 2 & -7 & 5 \\ 2 & 1 & -3\end{array}\right|=\hat{\mathrm{i}}(16)-\hat{\mathrm{j}}(-16)+\hat{\mathrm{k}}(16) \\ & 16(\hat{\mathrm{i}}+\hat{\mathrm{j}}+\hat{\mathrm{k}}) \\ & \left|\overline{\mathrm{b}_1 \times \overline{\mathrm{b}_2\right|=16 \sqrt{3} \\ & \therefore\left(\overline{\mathrm{a}_2-\overline{\mathrm{a}_1\right) \cdot\left(\overline{\mathrm{b}_1-\overline{\mathrm{b}_2\right)=16[-4+16]=(16)(12) \\ & \text{ S.D. }=\frac{(16)(12)}{16 \sqrt{3}}=4 \sqrt{3} \\ & \end{aligned}