I was messing around proving the area of a circle using trigonometric substitution. However, I ended up with area = -πr^2.(adsbygoogle = window.adsbygoogle || []).push({});

In my integral I ended up using trigonometric substitution and setting x = r*cos(theta)

However, this yields x = -r*sin(theta)*d(theta).

When that's substituted back into my integral, I ended up with the negative value for area. Why is it that if I were to use a different angle theta and express x = r*sin(theta) that I end up with the correct area?

Thanks a lot, as always.

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# Trigonometric Substitution

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