Answer:
The average of any sine or cosine is cero (0).
Step-by-step explanation:
The average of a sine wave is the area under the curve. If you consider the total area as the summatory of the red and the blue part colored in the picture, the red area is the same as the blue area but with opposite sign. When you add both the result is cero (0). The RMS value means a value of a DC signal that may behave (in terms of power) like the original wave.