c語言用累加產生cos波的問題

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我的程式碼

    double fi[10]={0,31.25,500,2000,4000,44,220,440,1760,3960};
    double ai[10]={100,2000,1000,500,250,100,2000,1000,500,250};
    for(i = 0; i < sampTimes; i++){  

        double costemp=0;

        double t= (double)i/(double)fs;   //t=sampTimes/Hz
        for(int j=0;j<10;j++){                 //x(t)
        costemp=costemp+round(ai[j]*cos(2*M_PI*(double)fi[j]*(t-0.1j)));
        } 
        cosinedata[i]=costemp;                       
        fwrite(&cosinedata[i],sizeof(int16_t),1,fp);
        fflush(fp);

    }

錯誤結果

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