it's just a simple expression involving powers and square roots...
you'll need to include the Math library
the math functions work using doubles, so you'll need to define them
then you'll need to get those numbers from the user, (or a file it's up to you).
printf ("enter that value of the capacitor");
scanf ("%lf", c);
printf ("enter that value of the coil");
scanf ("%lf", l);
printf ("enter that value of the resistor");
scanf ("%lf", r);
then you just need to write down the expression...
square rout in C is done like this,
result = sqrt(number);
powers are done like this
result = pow( number, power);
f = (sqrt(1/(l*c))) - sqrt((pow(r, 2)/(4*pow(c, 2)));
then output f
printf("Frequency = %lf", f);
This isn't tested fully, but I don't immediatly see any reason that it won't work...
I suspect that this is home work help,
you can hand this in if you like, but it won't recieve a great mark,
the program is not fool proof, I suggest that you look at the scanf statements, you can put anything into scan f, including multiple numbers, letters, huge numbers etc...
you should put a bit of error checking in there to complete the program properly...