Compiling question math lib c++
<p>I'm having trouble compiling some code for a class....<br>
this is where i'm having trouble</p>

<pre><code> aavg=0; int count=0;
    for(int i=0; i&lt;num;i++)
    {
    if ((math.abs(a[i])&lt;25.0)
    {
 count++;
 aavg+=a[i];                            
     }
     } 
 aavg=aavg/count;
 cout &lt;&lt; "The average a value in range, absolute value of a is less than 25.0 is: "&lt;&lt; aavg &lt;&lt;endl;
</code></pre>

<p>This is my whole program </p>

<pre><code> #include &lt;iostream&gt;
    #include &lt;fstream&gt;
    #include &lt;math.h&gt;
    #include &lt;cmath&gt;
    using namespace std;
    int main (void)
    {
        ifstream input ("measurements");
        int num=0;
        input &gt;&gt; num;
        float a[num];
        float b[num];
        float c[num];
        for(int i=0; i&lt;num;i++)
        input &gt;&gt; a[i] &gt;&gt; b[i] &gt;&gt; c[i];
        //All DATA IN
        //Do A AVERAGE
        float aavg =0;
        for(int i=0; i&lt;num;i++)
        aavg+=a[i]; 
        aavg=aavg/num;
        cout &lt;&lt; "A average: " &lt;&lt; aavg &lt;&lt;endl;
        //DO SMALLEST B
        float smallb=b[0];
        for(int i=1; i&lt;num; i++)
        if(smallb&gt;b[i])
        smallb=b[i];
        cout &lt;&lt;"Smallest b: " &lt;&lt;smallb &lt;&lt;endl;
        //PRINT ALL GISMO NUMBERS WHERE "a+c&lt;60.0
            for(int i=0; i&lt;num;i++)
            if((a[i]+c[i])&lt;60.0)
         cout &lt;&lt;"Gismo number " &lt;&lt;i &lt;&lt;" has a and c values that total less than 60" &lt;&lt;endl;
        //PRINT SMALLEST C VALUE BETWEEN 25.0 AND 50.0
          float smallc=51;
          for(int i=0; i&lt;num;i++)  
          if((25.0&lt;c[i])&amp;&amp;(c[i]&lt;50))
          if(smallc&gt;c[i])
          smallc=c[i];
          if(smallc&gt;50)
          cout &lt;&lt;"No values in range" &lt;&lt;endl;
          else
          cout &lt;&lt;"Smallest c in range was: "&lt;&lt;smallc &lt;&lt;endl;
          //LAST PART! woot!
          aavg=0; int count=0;
        for(int i=0; i&lt;num;i++)
        {
        if ((math.abs(a[i])&lt;25.0)
        {
     count++;
     aavg+=a[i];                            
         }
         } 
     aavg=aavg/count;
     cout &lt;&lt; "The average a value in range, absolute value of a is less than 25.0 is: "&lt;&lt; aavg &lt;&lt;endl;
     //system("PAUSE");
    }
</code></pre>
