积分函数的算法，一个非常好的实现，大家可以参考参考

用梯形公式和simpson公式求积分-with trapezoidal formula and simpson formula quadratures

用C语言实现变步长复合梯形求积分，变步长辛普森法求积分，高斯法求积分。-In the C language realization become step length composite trapezoid for integral, become step length Simpson method for integral, gaussian method for integral.