Convert double to Char/

[prog_tom]

Hello, I'm trying to convert a double to a char. how to acomplish that?

double t=sqrt(10)
MessageBox(NULL,t,"",0);

Always gives me an error, cannot convert double to char. Please give advice on how to solve this. Also, when I'm trying to use strcpy and strcat

double t=sqrt(10)
char T[MAX_LENGTH];
strcpy(T,"Hello this number is: ");
strcat(T,t);

Won't work. How to solve this as well? Thanks.