MCQ
Angle between the lines $2x - y - 15 = 0$ and $3x + y + 4 = 0$ is .....$^o$
  • A
    ${90}$
  • ${45}$
  • C
    ${180}$
  • D
    ${60}$

Answer

Correct option: B.
${45}$
b
(b)Lines are $2x - y - 15 = 0$ .....(i)
and $3x + y + 4 = 0$ ......(ii)
Here, ${m_1} = 2,\,{m_2} = - \,3$
If angle between them is $\theta $, then
$\tan \theta = \left| {\frac{{{m_1} - {m_2}}}{{1 + {m_1}{m_2}}}} \right|$ $ = \left| {\frac{{2 + 3}}{{1 - 6}}} \right| = \left| {\frac{5}{{ - 5}}} \right|$= 1
$\tan \theta = \tan \frac{\pi }{4}$ ==> $\theta = \frac{\pi }{4} = 45^\circ .$

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