E0562310 using sqrt() with RX210

Hello,

I created a project with e2 Studio V7.5 + CC-RX V2.08 for my RX210 controller.

Now I want to use function sqrt():, 

#include <math.h>
void main(void)
{
   float help=sqrt(19);
}

 

I get this error message:

E0562310:Undefined external symbol "_sqrt"

 

Do I have to set a special setting?

 

Thank you

Ralf