double gauss_ch2(double(*f)(double), int n);Gauss-Chebyeshev II 积分 double comp_gauss_leg(double (*f)(double), double a, double b)逐次减半Gauss-legender两点求积 double comp_trep(double (*f)(double), double a, double b) double romberg(double (*f)(double), double a, double b)