An alternating current is given by the equation \[i={{i}_{1}}\cos \omega \,t+{{i}_{2}}\sin \omega \,t\]. The r.m.s. current is given by [MP PMT 1994]

• A.            \[\frac{1}{\sqrt{2}}({{i}_{1}}+{{i}_{2}})\]
• B.            \[\frac{1}{\sqrt{2}}{{({{i}_{i}}+{{i}_{2}})}^{2}}\]
• C.            \[\frac{1}{\sqrt{2}}{{(i_{1}^{2}+i_{2}^{2})}^{1/2}}\]
• D.            \[\frac{1}{2}{{(i_{1}^{2}+i_{2}^{2})}^{1/2}}\]