If the shortest distance between the lines $\frac{x-\lambda}{3}=\frac{y-2}{-1}=\frac{z-1}{1}$ and $\frac{x+2}{-3}=\frac{y+5}{2}=\frac{z-4}{4}$ is $\frac{44}{\sqrt{30}}$, then the largest possible value of $|\lambda|$ is equal to _________.
Answer (integer)
43
Solution
<p>$$\begin{aligned}
& L_1: \frac{x-\lambda}{3}=\frac{y-2}{-1}=\frac{z-1}{1} \\
& L_2: \frac{x+2}{-3}=\frac{y+5}{2}=\frac{z-4}{4}
\end{aligned}$$</p>
<p>$$\begin{aligned}
& n_1 \times n_2=\left|\begin{array}{ccc}
\hat{i} & \hat{j} & \hat{k} \\
3 & -1 & 1 \\
-3 & 2 & 4
\end{array}\right| \\
& =-6 \hat{i}-15 \hat{j}+3 \hat{k} \\
& d=\left|\frac{[(\lambda+2) \hat{i}+7 \hat{j}-3 \hat{k}][-6 \hat{i}-15 \hat{j}+3 \hat{k}]}{|-6 \hat{i}-15 \hat{j}+3 \hat{k}|}\right|=\frac{44}{\sqrt{30}} \\
& \left|\frac{-6 \lambda-12-105-9}{\sqrt{270}}\right|=\frac{44}{\sqrt{30}} \\
& |6 \lambda+126|=132 \\
& |\lambda+21|=22 \\
& \lambda+21= \pm 22 \\
& |\lambda|_{\max }=43
\end{aligned}$$</p>
About this question
Subject: Mathematics · Chapter: Three Dimensional Geometry · Topic: Direction Cosines and Ratios
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