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Reply 40
Avatar for Lychee628
Lychee628
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19
Original post by SeanFM
As long as you see the point I am trying to illustrate. Eg domain (for real values of x) of
Unparseable latex formula:

\sqrtx

= ..

Go away, potentially dangerous latex message! :hand:


Its not showing it
Original post by Ayaz789
Its not showing it


I am a disaster with latex :colondollar: I have fixed it now but it is on the other page.. it was x\sqrt x.
Reply 42
Avatar for Lychee628
Lychee628
OP
19
Original post by SeanFM
I am a disaster with latex :colondollar: I have fixed it now but it is on the other page.. it was x\sqrt x.


What about the root of x?
Original post by Ayaz789
What about the root of x?


The domain of y=xy=\sqrt x in the reals is..
Reply 44
Avatar for Lychee628
Lychee628
OP
19
Original post by SeanFM
The domain of y=xy=\sqrt x in the reals is..


Im sorry but i dont understand what you are saying do you mean [1,infinity)
Original post by Ayaz789
Im sorry but i dont understand what you are saying do you mean [1,infinity)


I am asking you to find the range of values that you can put into that equation (i.e, the domain) and express it in terms of [] or (] or whatever the correct parentheses are.
Reply 46
Avatar for Lychee628
Lychee628
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19
Original post by SeanFM
I am asking you to find the range of values that you can put into that equation (i.e, the domain) and express it in terms of [] or (] or whatever the correct parentheses are.


Is it not [1, infinity) though?
Original post by Ayaz789
Is it not [1, infinity) though?


the infinity is a can of worms once more.. perhaps I should have not picked that. But 1 is not the right value. (Eg sqrt0.25 = 0.5 which exists).
Reply 48
Avatar for Lychee628
Lychee628
OP
19
Original post by SeanFM
the infinity is a can of worms once more.. perhaps I should have not picked that. But 1 is not the right value. (Eg sqrt0.25 = 0.5 which exists).

Yeah i know that but just stay with whole numbers for now, i thought infinity is always a curved bracket?
Original post by Ayaz789
Yeah i know that but just stay with whole numbers for now, i thought infinity is always a curved bracket?


That's not how it works - you can't exactly 'stay with the whole numbers' - if the function exists for x=0.25 for example then that's going to be part of your domain.

And I do not know.. I have never studied such things :redface: I guess it makes sense though.
Reply 50
Avatar for Lychee628
Lychee628
OP
19
Original post by SeanFM
That's not how it works - you can't exactly 'stay with the whole numbers' - if the function exists for x=0.25 for example then that's going to be part of your domain.

And I do not know.. I have never studied such things :redface: I guess it makes sense though.
just saying infinity is always a curved bracket:smile: ahh okay nw! Anyways im going sleep so ill message you tomorrow:biggrin:
Reply 51
Avatar for Zacken
Zacken
22
Original post by SeanFM

And I do not know.. I have never studied such things :redface: I guess it makes sense though.


The reason that you always use the curved brackets is because []/() notation is shorthand for [a,b][a, b] being {x∈R:a≤x≤b}\{x \in \mathbb{R} : a \leq x \leq b\}.

But a problem comes up when you trying b=∞b=\infty because then you require x=b∈Rx=b \in \mathbb{R} but infinity is not a member of the reals, so you can't say x=bx=b, i.e: it can't be inclusive. It has to exclude ∞\infty with a a≤x<∞a \leq x < \infty. i.e: the curved bracket.
(edited 7 years ago)

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