phase lock loop part 1

[vmcdonal]

equation 4 on the top of page 9:

Don't see how the integral of Se(t) is equal to Se(t)t??

[clint edwards]

It is assumed that Se(t) is varying slowly with respect to time, thus int(Se(t)*dt) can be aproximated as Se*t were t is the length of the integral and Se is the value of Se(t) at some time t.