It is known to exist deep. They can be expressed on through another. Harmonic oscillation degenerates into exp attenuation. It seems, I have finally comprehended it.
Any two magnitudes are related as sin and cos if the one is a growth of another. The exponent is a speed of change of itself.
In other words, I believe that a=sint and b=cost follows from the system
(1) a′(t) = b(t)
(2) b′(t) = k * a(t)
like f = e^x follows from the f(t)′ = f(t).
The angle Phi in exp(i*phi) signifies the balance between self-dependence and interdependence. Moving from zero (e^0) to in the imaginary cycle we shift to two-variables (e^i=sin) system and moving further we return to single-variable (e^(i*i)=e^-1)
Disclaimer: I'm a profane in the math. The philosophy must be taken as a prompt to study it.