Re: Error in FullSimplify
- To: mathgroup at smc.vnet.net
- Subject: [mg122955] Re: Error in FullSimplify
- From: Bob Hanlon <hanlonr357 at gmail.com>
- Date: Fri, 18 Nov 2011 06:23:36 -0500 (EST)
- Delivered-to: l-mathgroup@mail-archive0.wolfram.com
- References: <201111171104.GAA22782@smc.vnet.net>
This appears to have been fixed in version 8.
$Version
"8.0 for Mac OS X x86 (64-bit) (October 5, 2011)"
expr = (-E^((a + b I) x) + E^((a - b I) x) + E^((-a + b I) x) -
E^((-a - b I) x));
expr /. {a -> 3, b -> 4} // FullSimplify
-4 I Sin[4 x] Sinh[3 x]
expr /. {a -> 3., b -> 4.} // FullSimplify
2 (Cos[(4. + 3. I) x] - Cosh[(3. + 4. I) x])
% // Rationalize // Simplify
-4 I Sin[4 x] Sinh[3 x]
In both v7 and v8 on a Mac you can simplify this symbolically as follows.
expr // ExpToTrig // Simplify
-4 I Sin[b x] Sinh[a x]
Bob Hanlon
On Thu, Nov 17, 2011 at 6:04 AM, <"Philipp Wei=DFgraeber"@smc.vnet.net> wrote:
> Hello
>
> I have experienced some strange error in the FullSimplify-function in
> Mathematica 7.
>
> Input:
> (-E^((a+b I)x)+E^((a-b I)x)+E^((-a+b I)x)-E^((-a-b I)x))/.a->3 /.b->4 //
> FullSimplify
> (-E^((a+b I)x)+E^((a-b I)x)+E^((-a+b I)x)-E^((-a-b I)x))/.a->3. /.b->4.
> // FullSimplify
>
> Output:
> -4 I Sin[4 x] Sinh[3 x]
> -2 I Sin[4. x] Sinh[3. x]
>
> And the later result is wrong.
>
> What happens here, how can this be explained?
>
> CU
>
> Philipp
- References:
- Error in FullSimplify
- From: Philipp Weißgraeber@smc.vnet.net
- Error in FullSimplify