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How do you do this Question ?

  • 12-06-2011 4:17pm
    #1
    BmxNoob
    Registered Users, Registered Users 2 Posts: 55 ✭✭


    Quick question , Cant remember how to do this pass maths Q :

    The circle c has equation x² + y² =17.
    l is the line x – 4y – 17 = 0.
    The line l is a tangent to c at the point T.
    (i) Find the co-ordinates of T.


    Any help ?
    Thanks


Comments

  • #2
    LilMissCiara
    Registered Users, Registered Users 2 Posts: 2,292 ✭✭✭LilMissCiara


    BmxNoob wrote: »
    Quick question , Cant remember how to do this pass maths Q :

    The circle c has equation x² + y² =17.
    l is the line x – 4y – 17 = 0.
    The line l is a tangent to c at the point T.
    (i) Find the co-ordinates of T.


    Any help ?
    Thanks

    Do simultaneous equation with the 2!


  • #3
    partyatmygaff
    Registered Users, Registered Users 2 Posts: 10,992 ✭✭✭✭partyatmygaff


    Two methods.

    Find the slope of the tangent. Implicitly differentiate the circle function and then let dy/dx = slope of tangent.

    Or

    Simultaneous equations.


  • #4
    Ficheall
    Registered Users, Registered Users 2 Posts: 9,034 ✭✭✭Ficheall


    How does the simultaneous equations method work?


  • #5
    PJelly
    Closed Accounts Posts: 494 ✭✭PJelly


    Ficheall wrote: »
    How does the simultaneous equations method work?

    The line x – 4y – 17 = 0. So X= 17 + 4y.
    Sub that in for X in the circle and solve for Y. Then use that value to solve for X in your line.
    Voila. Marks


  • #6
    Shanee.
    Registered Users, Registered Users 2 Posts: 1,208 ✭✭✭Shanee.


    Ficheall wrote: »
    How does the simultaneous equations method work?

    Its more substitution that simultaneous equations.


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