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MHT CET · Maths · Straight Lines

If the angle between the lines is \(\frac{\pi^c}{4}\) and slope of one of the lines is \(\frac{1}{2}\), then slope of the other line is

  1. A 3 or \(-\frac{1}{3}\)
  2. B 4 or \(-\frac{1}{4}\)
  3. C 2 or \(-\frac{1}{2}\)
  4. D 3 or -3
Verified Solution

Answer & Solution

Correct Answer

(A) 3 or \(-\frac{1}{3}\)

Step-by-step Solution

Detailed explanation

We have \(\theta=45^{\circ}\) and \(\mathrm{m}_1=\frac{1}{2}\)
\(
\begin{aligned}
& \tan \theta=\left|\frac{\mathrm{m}_1-\mathrm{m}_2}{1+\mathrm{m}_1 \mathrm{~m}_2}\right| \\
& \therefore \quad \tan 45^{\circ}=\left|\frac{\frac{1}{2}-\mathrm{m}_2}{1+\left(\frac{1}{2}\right) \mathrm{m}_2}\right| \Rightarrow\left|\frac{1-2 \mathrm{~m}_2}{2+\mathrm{m}_2}\right|= \pm 1 \\
& \therefore \quad 1-2 \mathrm{~m}_2=2+\mathrm{m}_2 \text { or } 1-2 \mathrm{~m}_2=-2 \\
& \therefore \mathrm{m}_2=\frac{-1}{3} \text { or } \mathrm{m}_2=3
\end{aligned}
\)
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