An Alternating Current is expressed as $$i = i_1\cos\omega t + i_2\sin\omega t$$. The RMS value of current is

A

$$\sqrt{\frac{(i_1 + i_2)^2}{2}}$$

B

$$\sqrt{\frac{i_1 i_2}{2}}$$

C

$$\sqrt{\frac{i_1^2 + i_2^2}{2}}$$

D

$$\frac{\sqrt{(i_1 - i_2)^2}}{2}$$