[计] approximate expression ；
[例句] 这些公式使得这些点子上的导数近似式是非对称形式. These formulas make the approximations for the derivatives at these points in a nonsymmetrical manner.
[例句] 就准确度而言, 本研究所推导之近似式优于其他文献中所发表之相关公式. In terms of accuracy, the present approximation is superior to the previously reported ones.