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STD 11 - 9. straight line — Maths STD 11 Science — Question

CBSE BoardEnglish MediumSTD 11 ScienceMathsSTD 11 - 9. straight line1 Mark
MCQ
The angle between the lines $2x - y + 3 = 0$ and $x + 2y + 3 = 0$ is ...........  $^\circ$
  • ✓
    $90$
  • B
    $60$
  • C
    $45$
  • D
    $30$
✓

Answer

Correct option: A.
$90$
a
(a)Angle between two lines is given by $\tan \theta = \frac{{{m_1} - {m_2}}}{{1 + {m_1}{m_2}}}$
Given ${m_1} = \frac{{ - 1}}{2},$ ${m_2} = 2$ $\therefore \,\,{m_1}{m_2} = - 1$.
So the lines are perpendicular i.e., $\theta = 90^\circ $.

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