Electronics > Beginners

Exponents

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ebastler:

--- Quote from: Buriedcode on April 11, 2019, 01:52:11 pm ---I'm still unsure why this thread has so many replies
...
If the OP struggles with where to use parenthesis (I'm not suggesting he does, I don't know) then playing around with Excel can be handy, as that is quite strict in its use of them.

--- End quote ---

You are nicely illustrating why there are so many replies here. Besides people being chatty (myself included), some posters don't read the previous posts carefully and then make comments which add to the confusion.  :P

Excel was one of the very few examples highlighted in this thread which got operator precedence wrong, compared to mathematical convention. So playing around with Excel is not the recommended way to learn about mathematical notation conventions.

Buriedcode:

--- Quote from: tggzzz on April 11, 2019, 02:20:59 pm ---
--- Quote from: Buriedcode on April 11, 2019, 01:52:11 pm ---I'm still unsure why this thread has so many replies (I'm aware I'm adding to this!).  Precedence is indeed important and despite what nominal animal suggested, I'm pretty sure almost all "mathematicians" could state the order, perhaps with the acronyms BODMAS or PEDMAS.  Especially as it is so fundamental to even basic algebra. 

Whilst the average Joe who was taught this in basic mathematics has probably forgotten because most simply do not need to use this, I am willing to bet Engineers will be more likely to know this.

--- End quote ---

Engineers ought to. I wouldn't bet on UK primary school teachers knowing though :(


--- End quote ---

Why would they need to know?  Whilst I vaguely remember learning some algebra in primary school, I'm not sure it was required.  Why pick on primary school teachers?  They have an ever growing work load and constant changes to curriculum from a government who wants "all UK children to be above average"  :-DD (Direct quote from Michael Gove there).

I have noticed a lot of threads that deal with education or the basics of engineering/mathematics have this air of "in my day things were better" from the older generation.  Of course people are going to think that, because otherwise it implies that their education - and by extension, themselves - is/was substandard or outdated.  It doesn't mean that we are in fact "going backwards", it just appears that way as we get older, because of inevitable changes to education.



--- Quote from: tggzzz on April 11, 2019, 02:20:59 pm ---
--- Quote from: Buriedcode on April 11, 2019, 01:52:11 pm ---If the OP struggles with where to use parenthesis (I'm not suggesting he does, I don't know) then playing around with Excel can be handy, as that is quite strict in its use of them. 

--- End quote ---

It may be strict, but it is wrong (except within its own self-contained world). Shades of "Through the Looking Glass":

--- End quote ---


As for Excel being wrong, I guess this is what the bulk of the replies are about. What one considers to be right.  According to my Excel, -3^4 = 81.  Which I believe to be correct. And -(3^4) = -81. Also correct. So I'm not sure what your point is? 

tggzzz:

--- Quote from: Buriedcode on April 11, 2019, 02:59:11 pm ---
--- Quote from: tggzzz on April 11, 2019, 02:20:59 pm ---
--- Quote from: Buriedcode on April 11, 2019, 01:52:11 pm ---I'm still unsure why this thread has so many replies (I'm aware I'm adding to this!).  Precedence is indeed important and despite what nominal animal suggested, I'm pretty sure almost all "mathematicians" could state the order, perhaps with the acronyms BODMAS or PEDMAS.  Especially as it is so fundamental to even basic algebra. 

Whilst the average Joe who was taught this in basic mathematics has probably forgotten because most simply do not need to use this, I am willing to bet Engineers will be more likely to know this.

--- End quote ---

Engineers ought to. I wouldn't bet on UK primary school teachers knowing though :(


--- End quote ---

Why would they need to know?  Whilst I vaguely remember learning some algebra in primary school, I'm not sure it was required.  Why pick on primary school teachers?  They have an ever growing work load and constant changes to curriculum from a government who wants "all UK children to be above average"  :-DD (Direct quote from Michael Gove there).

I have noticed a lot of threads that deal with education or the basics of engineering/mathematics have this air of "in my day things were better" from the older generation.  Of course people are going to think that, because otherwise it implies that their education - and by extension, themselves - is/was substandard or outdated.  It doesn't mean that we are in fact "going backwards", it just appears that way as we get older, because of inevitable changes to education.



--- Quote from: tggzzz on April 11, 2019, 02:20:59 pm ---
--- Quote from: Buriedcode on April 11, 2019, 01:52:11 pm ---If the OP struggles with where to use parenthesis (I'm not suggesting he does, I don't know) then playing around with Excel can be handy, as that is quite strict in its use of them. 

--- End quote ---

It may be strict, but it is wrong (except within its own self-contained world). Shades of "Through the Looking Glass":

--- End quote ---


As for Excel being wrong, I guess this is what the bulk of the replies are about. What one considers to be right.  According to my Excel, -3^4 = 81.  Which I believe to be correct. And -(3^4) = -81. Also correct. So I'm not sure what your point is?

--- End quote ---

Using similar reasoning, I consider 6*9=42 to be correct, because it is correct.

But that's not very helpful, and could be considered peverse.

ebastler:

--- Quote from: Buriedcode on April 11, 2019, 02:59:11 pm ---As for Excel being wrong, I guess this is what the bulk of the replies are about. What one considers to be right.  According to my Excel, -3^4 = 81.  Which I believe to be correct. And -(3^4) = -81. Also correct. So I'm not sure what your point is?

--- End quote ---

Grmpf. Just read the posts above.
Or read this, quoted a couple of times in this thread: https://en.wikipedia.org/wiki/Order_of_operations#Unary_minus_sign

Excel is one of the few programs which implements unary minus the wrong way, i.e. different from mathematical notation. The correct math is -34 = - (34) = -81.

Buriedcode:

--- Quote from: ebastler on April 11, 2019, 02:57:58 pm ---
--- Quote from: Buriedcode on April 11, 2019, 01:52:11 pm ---I'm still unsure why this thread has so many replies
...
If the OP struggles with where to use parenthesis (I'm not suggesting he does, I don't know) then playing around with Excel can be handy, as that is quite strict in its use of them.

--- End quote ---

You are nicely illustrating why there are so many replies here. Besides people being chatty (myself included), some posters don't read the previous posts carefully and then make comments which add to the confusion.  :P

Excel was one of the very few examples highlighted in this thread which got operator precedence wrong, compared to mathematical convention. So playing around with Excel is not the recommended way to learn about mathematical notation conventions.

--- End quote ---

Ok, I think I see your point.  The idea that the sign is in fact a multiplication by -1, so -34 should be -1*34, and because of precedence, the exponent should be calculated before multiplication, giving -1*81 = -81?  If we add parentheses around that assumption: (-1 * 3)4 then the answer is of course 81 - parentheses first, then exponent.

I still maintain that without parentheses, there is ambiguity. So the OP's original question has the answer: it depends.  As for excel being "wrong", anyone who doesn't use parentheses correctly is relying on whatever rules their software uses which as can be seen from this thread, varies.  As to which software is "right", again this depends on what rules it uses, and will just go around in circles of people saying "but but but its wrong!".

The take home message is - correct/strict use of parentheses isn't optional.  Complaining that software doesn't do things how you expect when you don't use them isn't the fault of the software, it is the fault of the user.

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