1. Calculus is a difficult course for most of the college students. ���ֶԴ�ѧ����˵��һ�ź��ѵĿγ̡�
2. In the refutation tree of predicate calculus, the proved conjunctive formula. ��ν������ķ������У���֤���ĺ�ʽ��ʽ��
3. Calculus is all about continuums �� rates of change, areas under curves, volumes of solids. ���ֶ��ǹ�������ͳ��--�仯�ı��ʣ����ߵ����������������
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n.
1. a hard lump produced by the concretion of mineral salts; found in hollow organs or ducts of the body
2. an incrustation that forms on the teeth and gums
3. the branch of mathematics that is concerned with limits and with the differentiation and integration