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Review the whole book Mathematics III
When we can't determine the specific figures, we can still determine the integral interval by roughly analyzing the general trend of the curve!

We don't know x/a under the root plus y/b= 1 under the root, but obviously, with the increase of X, Y will gradually decrease.

When x=0, the maximum value of y is obtained, and when y=b, similarly, the maximum value of x is a.

So we can be sure that this is both an X-shaped area and a Y-shaped area, and we don't need to know the specific graph to calculate it!

For example, we integrate y first, then x, ∫0, adx∫0, cydy, where c is determined by the curve equation (it can be said that it is not fun).

The rest is simple, just repeat the integral. The integral of y is easy to shoot. After the calculation, bring in x and then calculate the integral of x, which requires a simple substitution method.