Answer :
If the two currents (3sin(wt) and 4cos(wt)) are superimposed u would get 5sin(wt+Ф), where Ф is some phase lag.
The rms is then Maximum value / [tex] \sqrt{2} [/tex] = [tex] \frac{5}{ \sqrt{2} } [/tex]
The rms is then Maximum value / [tex] \sqrt{2} [/tex] = [tex] \frac{5}{ \sqrt{2} } [/tex]