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wildjay8
Group Title
Write the equation of a circle that has center (2,4) and passing through (4,1)
 2 years ago
 2 years ago
wildjay8 Group Title
Write the equation of a circle that has center (2,4) and passing through (4,1)
 2 years ago
 2 years ago

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timo86m Group TitleBest ResponseYou've already chosen the best response.1
r^2=(x2)^2+(y(4))^2 hold on i'll find r
 2 years ago

colorful Group TitleBest ResponseYou've already chosen the best response.0
why is it not\[r^2=(x+4)^2+(y2)^2\]?
 2 years ago

timo86m Group TitleBest ResponseYou've already chosen the best response.1
Use distance formula to find r sqrt((delta x)^2+(delta y)^2) delta x just means difference in x which is xfxi = 42 Same for delta y
 2 years ago

colorful Group TitleBest ResponseYou've already chosen the best response.0
oh no wait I remember...
 2 years ago

colorful Group TitleBest ResponseYou've already chosen the best response.0
the formula for a circle with center (h,k) is r^2=(yk)^2+(xh)^2
 2 years ago

timo86m Group TitleBest ResponseYou've already chosen the best response.1
more info http://www.regentsprep.org/Regents/math/algtrig/ATC1/circlelesson.htm
 2 years ago

wildjay8 Group TitleBest ResponseYou've already chosen the best response.0
there is no more info
 2 years ago

colorful Group TitleBest ResponseYou've already chosen the best response.0
yeah, but those links always confuse me and then how do you find r again, isn't there some easy way?
 2 years ago

timo86m Group TitleBest ResponseYou've already chosen the best response.1
Use distance formula to find r sqrt((delta x)^2+(delta y)^2) delta x just means difference in x which is xfxi = 42 Same for delta y
 2 years ago

colorful Group TitleBest ResponseYou've already chosen the best response.0
well they tell you the center of the circle, so we know h and k
 2 years ago

wildjay8 Group TitleBest ResponseYou've already chosen the best response.0
yes colorful you have it a little mixed around (xh)^2+(yk)^2=r^2
 2 years ago

colorful Group TitleBest ResponseYou've already chosen the best response.0
well whether you write (xh)^2+(yk)^2=r^2 or (yk)^2+(xh)^2=r^2 it's the same thing, isn't it? and the picture should be something like this dw:1337145806387:dw
 2 years ago

colorful Group TitleBest ResponseYou've already chosen the best response.0
so we want the radius r, and I think we can use the pythagorean formula from geometry to figure out how long it is...
 2 years ago

wildjay8 Group TitleBest ResponseYou've already chosen the best response.0
yes now i just have to write the equation
 2 years ago

wildjay8 Group TitleBest ResponseYou've already chosen the best response.0
i think we use d formula
 2 years ago

colorful Group TitleBest ResponseYou've already chosen the best response.0
well you only need to find r now we already know the rest just plug in the numbers for h and k into (xh)^2+(yk)^2=r^2
 2 years ago

wildjay8 Group TitleBest ResponseYou've already chosen the best response.0
radius would be 5 i think
 2 years ago

colorful Group TitleBest ResponseYou've already chosen the best response.0
we still gotta find r though is it 5 ? let me check...
 2 years ago

wildjay8 Group TitleBest ResponseYou've already chosen the best response.0
so final answer (x2)^2+(y+4)=5
 2 years ago

wildjay8 Group TitleBest ResponseYou've already chosen the best response.0
think thaty is right does that 4 become positive on the y
 2 years ago

colorful Group TitleBest ResponseYou've already chosen the best response.0
dw:1337146127268:dwI don't think the radius is 5 why do you think it's 5 ???
 2 years ago

wildjay8 Group TitleBest ResponseYou've already chosen the best response.0
d=square root of 42 +1(4) square root of 2+3 Square root of 5
 2 years ago

colorful Group TitleBest ResponseYou've already chosen the best response.0
\[d=\sqrt{(42)^2+(1(4))^2}=\sqrt{2^2+3^2}\]
 2 years ago

wildjay8 Group TitleBest ResponseYou've already chosen the best response.0
im coming up with (x2)^2+(y+4)^2=5 will someone verify or tell me where im wrong
 2 years ago

wildjay8 Group TitleBest ResponseYou've already chosen the best response.0
good thinking colorful i did that before
 2 years ago

colorful Group TitleBest ResponseYou've already chosen the best response.0
but it doesn't give 5...
 2 years ago

wildjay8 Group TitleBest ResponseYou've already chosen the best response.0
radius is 13
 2 years ago

wildjay8 Group TitleBest ResponseYou've already chosen the best response.0
which in my notes we had sqrt 18 we put radius as 18
 2 years ago

colorful Group TitleBest ResponseYou've already chosen the best response.0
um... don't know what to tell you about that, sorry :(
 2 years ago

colorful Group TitleBest ResponseYou've already chosen the best response.0
maybe there's a typo, or you copied something wrong?
 2 years ago

wildjay8 Group TitleBest ResponseYou've already chosen the best response.0
so answer would be (x2)^2+(y+4)^2=13
 2 years ago

colorful Group TitleBest ResponseYou've already chosen the best response.0
yeah, looks like it
 2 years ago

wildjay8 Group TitleBest ResponseYou've already chosen the best response.0
thank you colorful for helping and pointing out mistake
 2 years ago

colorful Group TitleBest ResponseYou've already chosen the best response.0
no problem :D welcome!
 2 years ago

robtobey Group TitleBest ResponseYou've already chosen the best response.0
A Mathematica version of the solution with comments and a plot is attached.
 2 years ago
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