An alternating current is given by $\mathrm{i}={\mathrm{i}}_{1 }\cos \mathrm{\omega t}+{\mathrm{i}}_2 \sin \mathrm{\omega t}$. The value of rms current is 

• A

  $\frac{{\mathrm{i}}_1+{\mathrm{i}}_2}{\sqrt{2}}$
• B

  $\frac{\left|{\mathfrak{i}}_1+{\mathfrak{i}}_2\right|}{\sqrt{2}}$
• Correct answer
  C

  $\sqrt{\frac{{\mathrm{i}}_1^2+{\mathrm{i}}_2^2}{2}}$
• D

  $\sqrt{\frac{{\mathfrak{i}}_1^2+{\mathfrak{i}}_2^2}{\sqrt{2}}}$

Hence, the correct answer is option: 'C'.