Re: Trigonometric simplification

*To*: mathgroup at smc.vnet.net*Subject*: [mg68881] Re: Trigonometric simplification*From*: carlos at colorado.edu*Date*: Tue, 22 Aug 2006 05:20:11 -0400 (EDT)*References*: <ecbnnc$r29$1@smc.vnet.net><ecc2pn$ajl$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

> Hi Carlos, > > Using TrigReduce before Simplify will do it: > > r = Tan[a]^2/(Sec[a]^2)^(3/2); > Simplify[TrigReduce[r], Assumptions -> {a > 0, Sec[a] > 0}] > > --> Cos[a]*Sin[a]^2 > > Best regards, > Jean-Marc Thanks, that works perfectly. Actually Sec[a]>0 as assumption is sufficient. This is correct from the problem source, since the angle is in the range (-Pi/2,Pi/2) Here is a related question. How can I get Mathematica to pass from d = 2 + 3*Cos[a] + Cos[3*a] (* leaf count 10 *) to 1 + 2*Cos[a]^3 (* leaf count 8 *) TrigExpand[d] gives 2 + 3*Cos[a] + Cos[a]^3 - 3*Cos[a]*Sin[a]^2 Applying Simplify to that yields 2 + 3*Cos[a] + Cos[3*a] so we are back to the beggining.

**Follow-Ups**:**Re: Re: Trigonometric simplification***From:*Andrzej Kozlowski <akoz@mimuw.edu.pl>

**Re: Re: Trigonometric simplification***From:*Daniel Lichtblau <danl@wolfram.com>