# Plotting circle equation in Wolfram|Alpha?

Posted 5 years ago
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 Hi,I was trying to plot circle equations and found a strange bug:When plotting following equation: 0.66^2 = (x-1)^2 + (y-1)^2 the circle is plotted correctly as expected.But when taking the square root first on both sides: 0.66 = sqrt((x-1)^2 + (y-1)^2) the circle printed has nearly double the radius as expected. Also I tried to verify if the radius is really "double" the expected one by plotting a vertical line in the same plot: 0.66 = sqrt((x-1)^2 + (y-1)^2), x = -1.32 This however plots the correct circle.When I'm missing something here, I apologize.Best regards!
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Posted 5 years ago
 Hi Mawe,Can you share the code as to how you are plotting these?I tried the following: ContourPlot[0.66^2 == (x - 1)^2 + (y - 1)^2, {x, 0, 2}, {y, 0, 2}] ContourPlot[0.66 == Sqrt[(x - 1)^2 + (y - 1)^2], {x, 0, 2}, {y, 0, 2}] And they came out the same circle.Cheers,Wilson
Posted 5 years ago
 Hi Wilson,I just went to https://www.wolframalpha.com/ and typed in exactly what I wrote in my first post.Best regards, Mawe
Posted 5 years ago
 Hi Mawe,Not sure why your replay isn't showing up.And my apology for not reading the tag of the post to know it's for W|A.If you look at the "bugged" plot carefully, the intersection of the x and y axis is actually not (0,0)... it intersects at (0.5, 0.5) [Why it defaults to that, I don't know]. But if you adjust the plot domain 0.66 = sqrt((x-1)^2 + (y-1)^2), x in (0, 2) You will get what you are looking for again.Cheers,Wilson
Posted 5 years ago
 Hi Wilson,and I really thought checking the axis 100 times is enough before writing this post.Next time I'll check 101 times.Thanks and best regards, Mawe