Re: Cancel order

• To: mathgroup at smc.vnet.net
• Subject: [mg123266] Re: Cancel order
• From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
• Date: Tue, 29 Nov 2011 07:40:59 -0500 (EST)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com
• References: <201111291205.HAA05469@smc.vnet.net>

```
On 29 Nov 2011, at 13:05, =E9=81=93 =E5=8E=9A wrote:

> How can I make Sqrt[(v1^2+v2^2)(g^2+gp^2)]/Sqrt[v1^2+v2^2] simple in
> mathematica?
>

You need the assumption that the expressions under the square root are positive. So:

Assuming[g^2 + gp^2 >= 0 && v1^2 + v2^2 > 0,
Simplify[Sqrt[(g^2 + gp^2)*(v1^2 + v2^2)]/Sqrt[v1^2 + v2^2]]]

Sqrt[g^2 + gp^2]

In particular, this will be true if everything in your expression is real:

Assuming[Element[_, Reals],
Simplify[Sqrt[(g^2 + gp^2)*(v1^2 + v2^2)]/
Sqrt[v1^2 + v2^2]]]

Sqrt[g^2 + gp^2]

Andrzej Kozlowski

```

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