Do not understand why

Do not understand why - Messages

#1 Posted: 1/7/2017 5:19:37 PM
Andrey Ivashov

Andrey Ivashov

2270 likes in 3734 posts.

Group: Super Administrator

Hello!

Does anybody can explain the result of this expression in wolfram alpha?

wa_example_1.png

Why Amperes are used for both operands in result?
#2 Posted: 1/7/2017 7:13:37 PM
Brian Runagle

Brian Runagle

13 likes in 27 posts.

Group: User

The input expression mixes unitless with units: 1(unitless) + 3i(units A)
so I guess it corrects this by using Amps throughout in the output.
Brian
#3 Posted: 1/7/2017 8:36:06 PM
Martin Kraska

Martin Kraska

1222 likes in 2150 posts.

Group: Moderator

Andrey, please don't adopt any silent correction behaviour for units in SMath. The rejection of expressions with non-matching units is very helpful.
Martin Kraska Pre-configured portable distribution of SMath Studio: https://en.smath.info/wiki/SMath%20with%20Plugins.ashx
1 users liked this post
Davide Carpi 1/8/2017 4:26:00 PM
#4 Posted: 1/7/2017 10:22:21 PM
Jean Giraud

Jean Giraud

983 likes in 6866 posts.

Group: User

Wolfram shows that the complex argument is ill posed
if associated with unit. You have it same way in Smath.

Jean

Andrey Wolfram Alpha.sm (4 KiB) downloaded 97 time(s).
#5 Posted: 1/8/2017 8:33:46 AM
Martin Kraska

Martin Kraska

1222 likes in 2150 posts.

Group: Moderator

Wrote

Wolfram shows that the complex argument is ill posed
if associated with unit. You have it same way in Smath.

Jean



Neither is the problem ill posed nor is it the same way in SMath. And Wolfram just acts like an over-eager spell-checker with making things worse while trying to make the units match.

If you take i as a variable of dimension 1/A then the units would match. Considering the input being wrong (or ill posed) would require
- i being strictly reserved for sqrt(-1) (which it is not in SMath)
- any variable (like i) being strictly dimensionless (which it is not in SMath)

Obviously both assumptions neither apply to Wolfram Alpha.

The only similarity in the behaviour between SMath and WA is that both assume i being the imaginary unit. Nothing wrong so far.

But is a clear complaint about non-matching units really "the same" as silently messing with the structure of the expression?










Martin Kraska Pre-configured portable distribution of SMath Studio: https://en.smath.info/wiki/SMath%20with%20Plugins.ashx
  • New Posts New Posts
  • No New Posts No New Posts