trapezoidal rule

usually, it is calculated approximately via trapezoidal rule, then the virtual value.

积分值与积分起始点的初相角无关，通常用梯形法则近似求出，然后求得有效值。

using trapezoidal rule, with 4 strips, work out how much poison she should buy. and use a large, clear diagram show the solution.

利用多边形法则，利用4组数据，算出需要多少农药，用一个清晰地图示展示解答。

Using the classical model and piece-wise linearization technique, this paper presents a novel method for fast numerical simulation and assessment of power system transient stability. The method adopts the implicit trapezoidal rule and the relaxation method instead of the direct but time-consuming matrix inversion.

在使用电力系统经典模型和分段线性化的基础上，本文利用隐式梯形积分规则并结合矩阵求逆运算的松驰方法，推导出一种电力系统暂态稳定性数值仿真及快速判断方法。