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Homework problem I recently got:

Find the length of the curve of $y=\sqrt{a^2-x^2}$ from $x=-2$ to $x=1$. Also find the area of the surface of revolution about the $x$-axis.

Having trouble understanding this. I'm not even sure what it would look like. I assume a is supposed to be a constant. Is it just a semi-circle with radius $a$. $X$-intercepts of $(-a,0)$ and $(a,0)$ and a max at $(0,a)$?

I'm a little iffy about how to first find the length.

I do know that I should start with $\int_{-2}^{1} 2\pi y ds$ since I am revolving about the x-axis.

Thanks for anyone who can help me out.

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