#### harry456

##### Member level 1

Ufm(t)=Uc*cos(2*pi*fc*t+Kfm*integral(0,t,m(t))

with m(t)=sin(2*pi*fm*t)

but the integral of sin(x) is -cos(x). And sin(90°)=1 cos(90°)=0, sin(270°)=-1 cos(270°)=0 ... What I don't get is: At max of m(t) (sin(x)) is the integral(m(t)) =0 that means the frequency is not increased or decreased but the idea behind FM is that at the max of m(t) the frequency should be at its extrema. What do I wrong or what do I not consider?