MCQ

If the two lines with slope m1 and m2 are perpendicular then their slopes has relation:

  • A
    m1 + m2 = 1
  • B
    m1 × m2 = 1
  • C
    m1 × m2 = -1
  • D
    m1 + m2 = -1

Answer

  1. m1 × m2 = -1

Solution:

If the two lines are perpendicular then if one line form angle $\alpha$ with positive x-axis then the other line form angle $90^\circ + \alpha$

If $\text{m}_{1} = \tan \alpha$ then m2 will be $\tan (90^\circ + \alpha) = -\cot\alpha = \frac{-1}{\tan\alpha}$

⇒ m1 × m2 = -1.

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