Let v(t)=Vm cos (ωt+θ);

Phasor of this is taken as V=Vm exp(jθ)

in phasor notation, V^2 = Vm exp(jθ) * Vm exp(jθ) = Vm^2 exp(2jθ) => v(t)^2= Vm^2 * (cos 2ωt+2θ)

But from trignomatry, v(t)^2 = Vm^2 * cos^(ωt+θ)

Why am i getting two different answers? Where have i gone wrong. Please give me an answer. Thanx