Results 1 to 4 of 4

Math Help - Tangent line

  1. #1
    Newbie
    Joined
    Feb 2009
    Posts
    20

    Tangent line

    the line y=ax + k is tangent to the circle xsquared + (y-4)squared at the point (4,6). What is the value of (a+k)?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    No one in Particular VonNemo19's Avatar
    Joined
    Apr 2009
    From
    Detroit, MI
    Posts
    1,823

    Maybe this'll help

    I would solve this problem by first understanding that the line tangent to the circle will be perpindicular to a line going through the given point, and the ceter of the circle, which can be found easily. Once you find the slope of the line through the center, all you have to do is insert the negative reciprocal into the eequation where you see (a), solve for k and the rest is history!
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Feb 2009
    Posts
    20
    ive drawn a blank. how do i go about finding the slope?
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Member
    Joined
    Apr 2009
    Posts
    166
    Draw your circle. Now draw a line from the origin to the point (4,6) on that circle. The line tangent to this point will be perpendicular to line you just drew. As such, the slope of the perpendicular must be -1/(m) for the slope of the drawn line.

    Like, if the line you drew had a slope of 2, the tangent would have a slope of -1/2.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 3
    Last Post: November 4th 2011, 07:42 PM
  2. Replies: 6
    Last Post: January 12th 2011, 03:38 PM
  3. Replies: 5
    Last Post: November 4th 2009, 07:49 PM
  4. tangent line & normal line question
    Posted in the Calculus Forum
    Replies: 4
    Last Post: March 15th 2009, 04:45 AM
  5. Replies: 4
    Last Post: March 17th 2008, 02:53 PM

Search Tags


/mathhelpforum @mathhelpforum