How Is Average DC Output Calculated for a Half-Wave Rectified Sine Wave?

[zigg]

Using calculus integrals, evaluate the average dc output of a complete cycle of a half-wave rectified sine wave. Express the average value of the voltage as the area under the voltage vs wt curve, divided by the baseline.

I am completely confused. Should I be using a frequency forumula like:
1/pie (integral of) F(theta) sin [(n)(theta)] d(theta)

 

[Delphi51]

Wouldn't the voltage be V = A*sin(2πft) for the first half period, and zero for the second half? Maybe it isn't necessary to use frequency at all since the frequency should cancel out in the end, but kind of nice to show that.