Find the equation of the sphere

  • Thread starter Whatupdoc
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  • #1
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Find the equation of the sphere centered at (-6,-7,-1) with radius 9.

well i got [tex](x+6)^2 + (y+7)^2 + (z+1)^2-9^2[/tex] which is correct.

now for the next question:

Give an equation which describes the intersection of this sphere with the plane [tex]z=0[/tex].

i dont understand how to do the second question at all, can someone help?
 

Answers and Replies

  • #2
128
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What you got must've been:
[tex](x+6)^2 + (y+7)^2 + (z+1)^2-9^2 = 0[/tex].

The equation that describes the intersection with the plane z = 0 must be:
[tex](x+6)^2 + (y+7)^2 + (0+1)^2-9^2 = (x+6)^2 + (y+7)^2 - 80 = 0 [/tex]
 
  • #3
99
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thanks alot, i get it now
 

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