Given the sawtooth wave function $ \,x(t)\, $:
Energy
Compute the energy from 0 to $ 2\pi $.
Since we're integrating from 0 to $ 2\pi $, we can treat this as a simple line $ \,y(t)=\frac{1}{\pi}t\, $.
Answer: $ \,\frac{8\pi}{3}\, $
Power
Computer the power from 0 to $ 2\pi $.
Answer: $ \,\frac{4}{3}\, $