Re: LF: RE: something for the weekend ??

[DL4YHF@aol.com]

Hi Andy and group,

forgotten to mention this in my questionable explanation:
For "adding" the 90° phase shift in the sin() and cos() arguments, it's most important that the arguments are positive, which is the case in
    2*cos(a)*sin(b)
but not necessarily in
    sin(a+b)-sin(a-b) .
With a = 2*pi*f_signal * t    and b = 2 * pi * f_lo * t,
(a-b) can be a negative value which gives the wrong phase offset when ADDING 90° = pi/2 .

Cheers, 
  Wolf.