用梯形法求定积分，对应于一个积分式就要有一段程序，不过可以改变程序的一小部分 来改变所要求的积分式,程序以y=xsinx为例。-For definite integral using the trapezoidal method, corresponding to an integral type must have a program, part of a small but can change the program to change the integral requirem