Think in a phasorial picture.
In-phase component (I) is the function that multiplies cos(ωct) i.e. 1 .
Quadrature component (Q) is the function that multiplies sin(ωct) i.e. 0.5*cos(ωmt).
The resultant phasor has almost constant amplitude and a phase that is practically 0.5*cos(ωmt) radians .
It is a PM signal whose modulating signal is cos(ωmt) and peak phase deviation 0-5 rad .
Alternatively, it can be a FM signal whose modulating signal is sin(ωmt) .
Regards
Z