(Cut the bar with width dx perpendicular to the X axis, the lower limit is the leftmost X, the minimum value of X. The upper limit is the rightmost X, the maximum value of X. For the bar with x = x ~ x10dx, perpendicular to the Y axis, cut it into small squares with height dy. The lower limit is the lower edge y=u(x) and the upper limit is the upper edge y=v(x), where u is a function of the lower edge of the skin and v is the skin. The function of the upper edge.

Extended data:

Infinitely entering mathematics is another feature of higher mathematics. Everything in the real world appears in a limited form, and infinity is a summary of their identity. Therefore, infinite entry into mathematics is the embodiment of high theorization and abstraction of mathematics. Infinity in mathematics appears in two forms: latent infinity and real infinity. In the limit process, the change of variables is infinite and belongs to the form of infinite potential. The existence of limit value reflects the real infinite process.

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