Advertisement
If you have a new account but are having problems posting or verifying your account, please email us on hello@boards.ie for help. Thanks :)
Hello all! Please ensure that you are posting a new thread or question in the appropriate forum. The Feedback forum is overwhelmed with questions that are having to be moved elsewhere. If you need help to verify your account contact hello@boards.ie

The angle between two lines

  • 18-01-2015 10:59pm
    #1
    Take Your Pants Off
    Registered Users Posts: 1,519 ✭✭✭


    I cannot figure out how to do this question even from using the example on the previous page of the questions.
    find the obtuse angle between the lines x-2y-1=0 and 3x-y+2=0


Comments

  • #2
    Daniel2590
    Registered Users Posts: 1,645 ✭✭✭Daniel2590


    Basically you want to find the slope of each line and then use the formula tan∅ = ± (m1-m2)/(1+m1m2). Angle is 135° :)


  • #3
    Peregrine
    Moderators, Education Moderators Posts: 26,403 Mod ✭✭✭✭Peregrine


    Damn you, Dan. I had the whole thing typed up in LaTeX code and everything :(


  • #4
    Take Your Pants Off
    Registered Users Posts: 1,519 ✭✭✭Take Your Pants Off


    Thank you so much for an amazing fast reply.
    and Nim thank you too ! :)


  • #5
    Daniel2590
    Registered Users Posts: 1,645 ✭✭✭Daniel2590


    Nim wrote: »
    Damn you, Dan. I had the whole thing typed up in LaTeX code and everything :(

    Haha the one time I actually visit this forum :pac:


  • #6
    Peregrine
    Moderators, Education Moderators Posts: 26,403 Mod ✭✭✭✭Peregrine


    Be careful with perpendicular lines. The product of the slopes of two perpendicular lines is -1, so the denominator becomes 0..and you don't wanna go there.

    If you don't realise they're perpendicular from the slopes, a 0 denominator should tell you.


  • Advertisement
Advertisement