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数学 / 牛顿《原理》数学部分 / Lemma 4 · curvilinear and rectilinear figures

引理 4 · 曲边图形与直边近似

Curved areas are compared by rectilinear pieces whose errors can be made negligible.

曲边面积靠直边小片比较,关键是误差能被压到可忽略。

Lemma 4 · curvilinear and rectilinear figures gives a geometric way to compare quantities at the edge of vanishing.

引理 4 · 曲边图形与直边近似 给出一种几何方法,用来比较即将消失的量。

Replace a small curved sector by a triangle and track the difference.

把一个很小的曲边扇形换成三角形,并追踪差额。

The replacement is allowed only because the difference disappears faster than the controlled comparison.

替换成立,是因为差额比正在控制的比较更快消失。

与阿基米德穷竭法 archimedes-selections/overview、极限思想史 math-meta/topic-limit-history、微积分发明史 math-meta/topic-calculus-invention、柯西严格化 cauchy-cours/overview 和牛顿代数面 newton-arithmetica/overview 对读。