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Math Help - write the equation

  1. #1
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    write the equation

    of a sphere witha center (1,4,-3) and tangent to the xz plane
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  2. #2
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    Quote Originally Posted by tiga killa View Post
    of a sphere witha center (1,4,-3) and tangent to the xz plane
    (x-1)^2 + (y-4)^2 + (z+3)^2 = r^2

    r is the distance from the point (1,4,-3) to the xz plane ... which I leave for you to figure out.
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  3. #3
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    Hello, tiga killa!

    Write the equaton of a sphere with center (1,4,-3) and tangent to the xz-plane
    We have the center . . . we just need the radius, right?

    Can you visualize the sphere?
    . . If it is tangent to the xz-plane, the radius is 4.

    Therefore: . (x-1)^2 + (y-4)^2 + (x+3)^2 \:=\:16

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  4. #4
    Junior Member Infophile's Avatar
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    Hello,

    You have just to find the radius of this sphere.

    It corresponds of the abscissa since it has to be tangent to (O_z).

    Hence \color{red}R=1 and thus the equation of the sphere is \color{red}(x-1)^2+(y-4)^2+(z+3)^2=1

    Edit : What I called (O_z) is the plan (Oyz), maybe the sphere is tangent to (Oxz) ?

    Last edited by Infophile; May 5th 2009 at 01:55 PM.
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