powering

[Nanyo]

hello I need help
I'm trying to do simple calc but I'm faling with all my tryings:

#include <iostream>
#include <math.h>
using namespace std;
int main()
{
float firstnum, secondnum, result;
char sign;
while(true)
{
cout << "first number:\n";
cin >> firstnum;
cout << "What do yo want to do: * / + - ^\n";
cin >> sign;
cout << "second number:\n";
cin >> secondnum;
if(sign == '*')
{
cout << "the result is:" << firstnum * secondnum << "\n\n";
}
if(sign == '+')
{
cout << "the result is:" << firstnum + secondnum << "\n\n";
}
if(sign == '-')
{
cout << "the result is:" << firstnum - secondnum << "\n\n";
}
if(sign == '/')
{
if(secondnum == 0)
{
cout << "invalid denominator" << "\n\n";
}
else
{
cout << "the result is:" << firstnum / secondnum << "\n\n";
}
}
if(sign == '^')
{
result == pow((float) firstnum, secondnum);
cout << result << "\n\n";
}
}
return 0;
}

this is my code (C++code blocks compiler)
and this is the error:
undefined reference to `pow(double, double)'

HELP!!! Thank you!
if you see this in some others topics just ignore it!
it was my fault but I'm new, sorry!

[AbstractionAnon]

Did you even read the response to one of your other posts?

Line 41: You're using the comparison operator (==), not the assignment operator (=).

PLEASE USE CODE TAGS (the <> formatting button) when posting code.
It makes it easier to read your code and also easier to respond to your post.
http://www.cplusplus.com/articles/jEywvCM9/