Results 1 to 2 of 2

Math Help - Is this true for all tangents to a circle?

  1. #1
    Newbie
    Joined
    Feb 2010
    Posts
    18

    Is this true for all tangents to a circle?

    Well, I was testing somethings out to try and find a particular point that is a tangent to a circle and I decided to try this. I'm not too sure whether it's right or not.

    I just want to know if this is true for all tangents to a circle?



    Uploaded with ImageShack.us

    Excuse the terrible picture. I just drew it in a rush on MS Paint. I am hoping you can decipher it.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Super Member
    earboth's Avatar
    Joined
    Jan 2006
    From
    Germany
    Posts
    5,829
    Thanks
    123
    Quote Originally Posted by StephenPoco View Post
    Well, I was testing somethings out to try and find a particular point that is a tangent to a circle and I decided to try this. I'm not too sure whether it's right or not.

    I just want to know if this is true for all tangents to a circle?

    Excuse the terrible picture. I just drew it in a rush on MS Paint. I am hoping you can decipher it.
    You've found a very special case which is only true if |\overline{CR}| = |\overline{CQ}|

    In general:
    1. Use the indicated blue triangle to determine the slope of the tangent:

    m_t=-\frac1{m_{radius}}~\implies~m_t=-\frac{X_P - X_C}{Y_P - Y_C}

    2. Use the triangle RCQ to determine the slope of the tangent:

    m_t=\frac{Y_Q-Y_R}{X_Q-X_R}

    Since X_R = X_C and Y_Q = 0 the 2nd equation becomes:

    m_t=\frac{-Y_R}{X_Q-X_C}

    3. You now can use these 2 equations to get some additional results.
    Attached Thumbnails Attached Thumbnails Is this true for all tangents to a circle?-krstang_steigung.png  
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Circle and tangents
    Posted in the Geometry Forum
    Replies: 5
    Last Post: July 16th 2009, 06:45 AM
  2. Tangents to circle
    Posted in the Geometry Forum
    Replies: 1
    Last Post: November 25th 2008, 04:49 AM
  3. [SOLVED] circle tangents
    Posted in the Geometry Forum
    Replies: 3
    Last Post: June 17th 2008, 01:17 PM
  4. Tangents of a Circle
    Posted in the Geometry Forum
    Replies: 4
    Last Post: March 9th 2008, 10:25 AM
  5. circle-tangents question
    Posted in the Trigonometry Forum
    Replies: 2
    Last Post: September 12th 2005, 05:43 PM

Search Tags


/mathhelpforum @mathhelpforum