I was just starting to get comfortable with integrals in the easy situations, and then with substitution in some of the more difficult cases. I thought it might be kind of fun to try and calculate pi with the area under the semi circle:(adsbygoogle = window.adsbygoogle || []).push({});

[tex]\begin{math}y=\sqrt{9-x^2}\end{math}[/tex]

I figured the proper integral for this would be:

[tex]\begin{math}4\int_0^3 \sqrt{9-x^2}\end{math}[/tex]

but then I realized I'm not fully equipped to take that anti derivative. Substitution never fully gets rid of the x, and I'm unaware of a standard anti derivative that could be used to calculate such an integral. How would you go about this?

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# I don't understand this integral

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