Why I see interruptions when drawing circles?

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@Cornel wrote:

Hello,

Why I see that interruptions from below when I draw circles?

Because you are using Primes "Quickplot" feature - even though you did not define  variable x, Prime creates the plot for you.
For this to do, Prime must chose a suitable number of x-values on its own, which it usually does quite well.

But in case of the half circles, to the left and right ends we would need a lot of x-values at a very close distance to get the plot done as expected and Prime simply doesn't do that.

Martin showed a fix by providing a range with very dense x-values. Drawback is that each half circle now consists of 20000 points. We would by far not need that many points in the center (around x=0) but as we need that density at the ends ...

Of course its better to use a different mathematical representation of the circle to do the plot.

Either use the quickplot feature again (t is not defined)

or use a range to have better control. This time the half circle consists of just 21 connected points, not 20000 🙂