如何在此代码上实现多个子间隔？

如何解决如何在此代码上实现多个子间隔？

我正在尝试在下面给出的数学假设下优化函数（它实际上将代码中的当前间隔分解为多个子间隔，但是我什至如何实现呢？）：

[数学理论]-众所周知，如果将间隔分解成更小的间隔，梯形法则将给出更准确的近似值，从而：I1 = [a; b1]，I2 = [b1; b2]，I3 = [b2; b3]，...，I n-1 = [b n-1，bn]其中bn = b。从上面编写一个使用您的NC.m代码实现此策略的程序。它应该能够完成任意n个任务。必须创建多少个子间隔才能在间隔[-3：0] 上获得下面列出的函数的“准确” 积分近似值？

%For this problem write a script file called NC.m that implements 
%the Newton-Cotes method of integration for an arbitrary function f(x). It
%should takes as inputs the function and the limits of integration [a: b] and
%output the value of the definite integral. Specifically,you should use the
%Trapezoid rule as presented in Equation (11.73)

function [f]= NC(a,b,fun) %newton-cotes 

%a and b are limits of integration 

%setting it up 
fa= fun(a); %y value for lower limit 
fb= fun(b); %y value for upper limit 

%the actual function 
f= (b-a)*(fa+fb)/2; 

end 

%Result from estimation 
%fun= @(x) normpdf(x)  
%[f]= NC(-3,fun)-  0.6051 

%not accurate when compared to results from actual calculation  
%syms x 
%f= normpdf(x); 

%a= -3;- lower limit 
%b= 0;- higher limit 

%int(f,a,b)- 0.4897 

请帮助。不胜感激！