Re: Rewriting of Trigonometric Functions
- To: mathgroup at smc.vnet.net
- Subject: [mg26858] Re: [mg26803] Rewriting of Trigonometric Functions
- From: "Carl K. Woll" <carlw at u.washington.edu>
- Date: Fri, 26 Jan 2001 01:27:12 -0500 (EST)
- References: <200101240918.EAA03580@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Thomas,
Try using the command TrigReduce, as in
TrigReduce[Sin[a]Sin[b]]
Cos[a - b] - Cos[a + b]
-----------------------
2
Carl Woll
Physics Dept
U of Washington
----- Original Message -----
From: "Thomas Engelhardt" <thomas-a.engelhardt at t-online.de>
To: mathgroup at smc.vnet.net
Subject: [mg26858] [mg26803] Rewriting of Trigonometric Functions
> Dear Mathgroup members,
>
> I have just started to use Mathematica and directly ran into a problem:
>
> I have rather lengthy expressions resulting from putting a sum of two
> sinusodial swings to the power of three (Two-tone Intermodulation).
> In order for me to recognise the contained frequencies I want Mathematica
to
> rewrite the contained Trigonometric functions in certain ways, namely
like:
>
> [sin(a)]^2 should be transformed into 1/2*(1+cos2x)
> and for higher powers accordingly.
>
> Furthermore:
> sin(a)*sin(b) should be changed to 1/2*[cos(a-b) - cos(a+b)]
>
> I have tried all kinds of "Expand" and "Trig..." operations but
Mathematica
> always keeps the powers on the trigonometric functions and doesn't change
> the multiplications either.
>
> Does anybody have an idea how I can get Mathematica to transform the
> expressions in the desired way?
>
> I appreciate your help!
> Thanks in advance.
>
> Kind Regards
>
> Thomas
> Munich, Germany
>
>
- References:
- Rewriting of Trigonometric Functions
- From: thomas-a.engelhardt@t-online.de (Thomas Engelhardt)
- Rewriting of Trigonometric Functions