Assisting FullSimplify

• To: mathgroup at smc.vnet.net
• Subject: [mg56143] Assisting FullSimplify
• From: "Hugh Goyder" <h.g.d.goyder at cranfield.ac.uk>
• Date: Sat, 16 Apr 2005 03:53:17 -0400 (EDT)
• Organization: University of Warwick, UK
• Sender: owner-wri-mathgroup at wolfram.com

```I started with the expression e1 below. FullSimplify does not make any
progress in making it simpler. By a mixture of working on parts of the
expression, luck and physical reasoning I worked out that the expression is
the same as that given in e2. (For example I knew the expression should be
real). Is there anyway that I could have directed FullSimplify to get from
e1 to e2, by for example setting options?

(Cutting and pasting the code below into a notebook will make it readable.
It may then be evaluated.)

Thanks

Hugh Goyder

e1 = (4*I*
E^(I*(a + b)*k)*(-E^(2*I*a*k) +
E^(2*I*(1 + ar)*k)))/(E^(2*I*(1 + a + ar)*k)*(-2 + Sr) +
E^(2*I*(a + b)*k)*(-2 + Sr) - E^(4*I*a*k)*Sr + E^(2*I*(1 + ar)*k)*Sr +
E^(2*I*(2*a + b)*k)*Sr - E^(2*I*(1 + ar + b)*k)*Sr -
E^(2*I*a*k)*(2 + Sr) - E^(2*I*(1 + a + ar + b)*k)*(2 + Sr))

e2 = -(Sin[(1 - a + ar)*k]/((-Cos[(1 + ar)*k])*Cos[b*k] +
Sr*Cos[a*k]*Sin[(1 - a + ar)*k]*Sin[b*k]))

FullSimplify[e1]

FullSimplify[e1 == e2]

LeafCount[e1]

LeafCount[e2]

```

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