You use this downward pointing triangle as the notation for the gradient.

用▽表示,这就是梯度的符号。

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To model inheritance on a class diagram, a solid line is drawn from the child class (the class inheriting the behavior) with a closed, unfilled arrowhead (or triangle) pointing to the super class.

为了在一个类图上建模继承，从子类(要继承行为的类)拉出一条闭合的，单键头(或三角形)的实线指向超类。

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For this, we set it up between two inward pointing monitors to create a triangle.

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