[問題] 請幫看一下我寫得程式哪裡錯了

看板C_and_CPP (C/C++)作者WaterPisces ( )時間16年前 (2009/11/25 21:40)推噓3(3推 0噓 18→)

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我用Dev-C++寫數值分析的作業不清楚哪邊寫錯了請版友指正內容是要用Halley's method 一直迭代求tanπx-6 = 0的數值解過程列表 2f(x_n)f'(x_n) Halley's method : x_n+1 = x_n - ---------------------------- 2[f'(x_n)]^2-f(x_n)f"(x_n) 初始值0 ,誤差小於10^(-6)時停止 --------------------------------- #include<iostream> #include<cmath> using namespace std; double func(double x); int main() { double a = 0.0,PI = 3.14159 ,tol = 1e-6; double fa;double dfa;double dfb;double ddfa; cout<<"===============Halley's Method==============="<<endl; cout<<"Step\t\tP\t\tError"<<endl; cout<<"---------------------------------------------"<<endl; for(int i=0;i++){ fa=func(a); dfa=(func(a+0.000001)-func(a))/0.000001; dfb=(func(a)-func(a-0.000001))/0.000001; ddfa=(dfa-dfb)/0.000002; a=a-2*fa*dfa/(2*dfa*dfa-fa*ddfa); cout<<i+1<<"\t\t"<<a<<"\t\t"<<fabs(2*fa*dfa/(2*dfa*dfa-fa*ddfa))<<endl; if(fabs(2*fa*dfa/(2*dfa*dfa-fa*ddfa))<tol){ system("pause"); return 0; } } system("pause"); } double func(double x){ double y; y=tan(PI*x-6); return y; } 依v大發現我的小錯修改了一下 compile error message 現在剩下有 "for(int i=0;i++)" expected `;' before ')' token `PI' undeclared (first use this function) ------------------------------------- 因為程設以前就學的不好然後現在幾乎還給老師了...orz 所以我是google到一個牛頓法的程式作修改的原程式 ------------------------------------------- #include <iostream> #include <math.h> using namespace std; double func(double x); //a=initial guess,n=maximum allowable iterations,tol=tolerance double a=8; double n=20; double tol=1e-5; int main(){ double fa;double dfa; cout<<"===============Newton's Method==============="<<endl; cout<<"Step\t\tP\t\tError"<<endl; cout<<"---------------------------------------------"<<endl; for(int i=0;i<n;i++){ fa=func(a); dfa=(func(a+0.00001)-func(a))/0.00001; a=a-fa/dfa; cout<<i+1<<"\t\t"<<a<<"\t\t"<<fabs(fa/dfa)<<endl; if(fabs(fa/dfa)<tol){ cout<<"Converge!!!"<<endl; system("pause"); return 0; } } cout<<"DO NOT Converge!!!!"<<endl; cout<<"Please try more steps of iteration or change another method!!!"<<endl; system("pause"); } double func(double x){ double y; y=5*x*x-6*x-10; return y; } ------------------------------------- -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 59.114.244.170

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