two lines are perpendicular only when...

Discussion in 'Math' started by PG1995, Nov 23, 2011.

  1. PG1995

    Thread Starter Active Member

    Apr 15, 2011
    753
    5
    Hi

    Please have a look on the attachment. You can find me query there. Please help me with it. Thank you.

    Regards
    PG
     
  2. mrmount

    Active Member

    Dec 5, 2007
    59
    7
    Er! But Tan 45 =1 and Tan 135 = -1. Hence m1.m2= -1.
     
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