积分符号(Signs for Definite Integrals)是莱布尼茨于1675年以“omn.l”表示l的总和(积分(Integrals)),而omn为omnia(意即所有、全部)之缩写。其后他又改写为 ∫,以“∫l”表示所有l的总和(Summa)。∫为字母s的拉长。此外,他又于1694年至1695年之间,于∫号后置一逗号,如 ∫,xxdx。至1698年,约.伯努利把逗号去掉,后更发展为现今之用法。
为了提醒我们是在封闭曲线上做积分,经常在积分符号上加个圆圈,告诉我们,这条曲线自我封闭。
To remind ourselves that we are doing it along a closed curve, very often we put just a circle for the integral to tell us this is a curve that closes on itself.
称之为区域R上fdA的二重积分,会向大家解释这些符号的含义的。
So, we'll call that the double integral of our region, R, of f of xy dA and I will have to explain what the notation means.
当计算二重积分时,要多了解这些符号的具体含义。
OK, we'll come up with more concrete notations when we see how to actually compute these things.
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