Since you did not include any errors that you are getting, I will come up with solutions based on some possible errors that you may be encountering.
- Plotting multiple plots on the same figure
Additionally, consider adding parentheses to the 1/2 term. You may be telling matlab to put pi in the denominator of 1/2, so be careful there.
- The outputted plot is not a sine wave
To create a sine function, use the built-in MATLAB function sin(). This automatically calculates the sine function using radians. To use degrees, use sind(). The plot you have here is a square root curve, not a sine wave.
- Unrecognized function or variable 'R'; unrecognized function or variable 'C'
You will get this error if you have not defined the constants in your equation for Z. If you have previously defined these constants in your script/function then you will likely not get this error. I brought this up because you didn't include where you defined R and C.