MATLAB: Wrong result in elipse equation

anonymous functionelipse

I have defined an anonymous function elipse
>> xCenter = 0.58;
>> yCenter = 590;
>> a = 0.02;
>> b = 200;
>> elipse = @(x,y) ((x-xCenter)^2)/a^2 + ((y -yCenter)^2)/b^2 - 1;
But the result it's wrong in some case like this:
>> x1 = 0.6;
>> y1 = 590;
>> elipse(x1, y1)
ans =
        1.77635683940025e-15
This result should be 0, I have to set something else to fix it? One correct example is:
>> x1 = 0.58;
>> y1 = 390;
>> elipse(x1, y1)
ans =
       0
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