Re: ExpToTrig with Real Numbers

*To*: mathgroup at smc.vnet.net*Subject*: [mg63347] Re: [mg63334] ExpToTrig with Real Numbers*From*: Bob Hanlon <hanlonr at cox.net>*Date*: Sat, 24 Dec 2005 16:02:56 -0500 (EST)*Reply-to*: hanlonr at cox.net*Sender*: owner-wri-mathgroup at wolfram.com

Clear[approx]; approx[expr_, n_:14]:= expr/.x_?NumericQ:>Round[10^n*x]/10.^n; expr=(-0.2624844042359744*I)* Cos[0.9512492197250393*t]+ (0.26248440423597375*I)* Cos[0.9512492197250397*t]- 0.2624844042359744* Sin[0.9512492197250393*t]- 0.26248440423597375* Sin[0.9512492197250397*t]; approx[expr]//Chop -0.52496880847194*Sin[0.95124921972504*t] Bob Hanlon > > From: "Blimbaum, Jerry CIV NSWC PC" <jerry.blimbaum at navy.mil> To: mathgroup at smc.vnet.net > Date: 2005/12/24 Sat AM 07:18:59 EST > Subject: [mg63347] [mg63334] ExpToTrig with Real Numbers > > > A calculation gives me the following as a part of the output that I see > on the screen: (i = Imaginary) > > -0.262484 i Exp[-0.951249 i t] + 0.262484 i Exp[0.951249 i t] > > I want to apply ExpToTrig and , of course, end up with 0 for the Cosine > part and - .262484*2 Sin [0.951249] for the Sine part ... > > instead I get (which I decided to look at output with InputForm) > > (-0.2624844042359744*I)*Cos[0.9512492197250393*t] + > (0.26248440423597375*I)*Cos[0.9512492197250397*t] - > 0.2624844042359744*Sin[0.9512492197250393*t] - > 0.26248440423597375*Sin[0.9512492197250397*t] > > I can see from this that the coefficients and exponent numbers are very > close but not identical although , I think, in theory they should be. > I'm not worried about the 10th decimal place. How do i get the result > I want in a general way? > > > thanks....jerry blimbaum > > >