I cannot figure out why the area of a section of a sphere used for integration is:(adsbygoogle = window.adsbygoogle || []).push({});

(r * dtheta) (r * sin(theta) * dphi) ???

where dtheta and dphi are the differential angles that subtend the arcs, which make up the sides of the rectangle used for the differential area.

I did an integral of theta from 0 to pi and phi from 0 to 2*pi and the result was the area of a sphere. That is the correct result if the above formula was the correct differential area.

I see that this formula is made up of the angle that subtends the arc (the dtheta or dphi) multiplied by the length of one of the triangle's legs. The "triangle" that I mention here is the triangle that has two legs from the center of the sphere to the arc that is one side of the area rectangle. I just don't know why this would be the correct differential area and not some other formula?

Thanks!

-xerxes73

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# Area section of a sphere used for integration?

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