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Expand[] on the RHS of a rule

• To: mathgroup at yoda.physics.unc.edu
• Subject: Expand[] on the RHS of a rule
• From: athos at warp.stanford.edu (Athos Kasapi)
• Date: Mon, 25 May 92 13:27:42 PDT

Has anybody found a way to work around the problem that Expand does not
work when it is on the right hand side of a rule?  For example, if I
define

p := Sqrt[ (a + b) (c + d) ]

and then apply the rule

p /. Sqrt[ x_ y_ ] -> Sqrt[ Expand[ x y ] ]

Then all I get back is

Sqrt[ (a + b)(c + d) ]

What I wanted was

Sqrt[ ac + ad + bc + bd ]

I'd appreciate any suggestions for getting around this.

Athos Kasapi