Results 1 to 4 of 4

Math Help - parametric equation question

  1. #1
    Member
    Joined
    Oct 2007
    Posts
    134

    parametric equation question

    Please explain how to do the following problem.
    Graph the following parametric equation. Identify the domain and range. Eliminate the parameter.
    x = sq.root of t
    y = 2 sq.root of t

    Thank you very much
    I did a table for
    t = 0, 1, 4, 9
    x = 0, 1, 2, 3
    y = 2, 1, 0, -1

    Positioned the dots (x,y), it's a line Domain (-infinity, +infinity), Range (-infinity, +infinity). When I eliminated the parameter, the equation is y=2-x
    Does it make any sense? Thank you again.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Nov 2008
    From
    France
    Posts
    1,458
    Hi

    Your work is OK except for the domain and range

    x=\sqrt{t} and y=2-\sqrt{t} are defined only for t \geq 0 which means x \geq 0 and y \leq 2

    Therefore the graph is not a complete line but a "semi-line" starting from the point (0,2)
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Senior Member Pinkk's Avatar
    Joined
    Mar 2009
    From
    Uptown Manhattan, NY, USA
    Posts
    419
    The domain is not (-\infty,\infty), and neither is the range.

    x=\sqrt{t} is only defined when t\ge 0, which means x\ge 0, so your domain is [0,\infty)

    Likewise, y=2-\sqrt{t} is only defined when t\ge 0, which means y\le 2, so the range of the function is (-\infty,2].

    The equation IS y=2-x, but we must restrict the domain to [0,\infty) because of the parameters we were initially given.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Member
    Joined
    Oct 2007
    Posts
    134

    Thank you

    running-gag and Pinkk,

    Thank you very much.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. test question (parametric equation)
    Posted in the Calculus Forum
    Replies: 1
    Last Post: December 5th 2011, 10:19 PM
  2. Parametric Equation - method question
    Posted in the Calculus Forum
    Replies: 5
    Last Post: January 27th 2011, 01:10 PM
  3. A parametric equation question?
    Posted in the Calculus Forum
    Replies: 1
    Last Post: March 24th 2009, 10:50 AM
  4. Parametric Equation Question
    Posted in the Advanced Algebra Forum
    Replies: 6
    Last Post: September 24th 2008, 05:56 PM
  5. [SOLVED] Parametric or Non-Parametric: That Is the Question!
    Posted in the Advanced Statistics Forum
    Replies: 2
    Last Post: February 21st 2008, 03:24 PM

Search Tags


/mathhelpforum @mathhelpforum