Competition - post a photo you've taken of nature >>

Core 3

So in the domain and range questions when do i use the ( brackets and [ brackets?
e.g http://pastpapers.download.wjec.co.uk/w14-mathematics-ms.pdf
P.16

Scroll to see replies

Reply 1

Alexion

Original post by Ayaz789

So in the domain and range questions when do i use the ( brackets and [ brackets?
e.g http://pastpapers.download.wjec.co.uk/w14-mathematics-ms.pdf
P.16

Generally square brackets are used when inclusive of a value and parentheses if excluding that value.

i.e. [1,2) is an interval that includes 1 but not 2.

Reply 2

Lychee628

Original post by Alexion

Generally square brackets are used when inclusive of a value and parentheses if excluding that value.

i.e. [1,2) is an interval that includes 1 but not 2.

Im sorry but i don't understand :frown:

Reply 3

Alexion

For example this in the markscheme:

is the range of values in between 1 and 1.5 that includes 1.5 but does not include 1.

Reply 4

Lychee628

Original post by Alexion

For example this in the markscheme:

is the range of values in between 1 and 1.5 that includes 1.5 but does not include 1.

But how do you know if it includes that number or not? And do you get deducted marks if you get them wrong?

Reply 5

Alexion

Original post by Ayaz789

But how do you know if it includes that number or not? And do you get deducted marks if you get them wrong?

It depends how you're working out the range/domain ~ whether it can take that value or not.

~ If it's asymptotic at a value, then the range won't include that value, so you use a parenthesis.
~ If it's a numerical maximum/minimum, it can take that value, so you'd use a square bracket.

I don't think they penalise for it, but better safe than sorry :cute:

Reply 6

Lychee628

Original post by Alexion

I should get 100 Ums hopefully if they don't penalise me for this but like i get mixed up with squares and curved brackets , so the way i see it is if you have like a value that doesn't have a proper value like infinity it will have a curved bracket or like if you put infinity in the bracket to get the range then it'll be curved bracket ygm?
Thankss anyways, much appreciated mathematician! :biggrin:

Reply 7

Zacken

Original post by Ayaz789

That's because

\infty

isn't a real number.

Reply 8

Lychee628

Original post by Zacken

That's because

\infty

isn't a real number.

Yeah ik

but like where else can i use a curved bracket , i really don't understand where to use them :L

Reply 9

Zacken

Original post by Ayaz789

Yeah ik

but like where else can i use a curved bracket , i really don't understand where to use them :L

Whenever you need to specify a non-inclusive interval.

Reply 10

Lychee628

Original post by Zacken

Whenever you need to specify a non-inclusive interval.

Like what do you mean by that? :redface:

Reply 11

Zacken

Original post by Ayaz789

Like what do you mean by that? :redface:

Like if I told you to write down the set of numbers between 1 and 2 that don't include the number 1 or 2.

Reply 12

Lychee628

Original post by Zacken

Like if I told you to write down the set of numbers between 1 and 2 that don't include the number 1 or 2.

If you told me to write a set of numbers between 1 and 2 that dont include 1 and 2 huh? Ill tell you an example to do , 1 min

Reply 13

IrrationalRoot

Original post by Ayaz789

Like what do you mean by that? :redface:

[a,b] means all the real numbers between a and b including a and b.
(a,b) means all the real numbers between a and b excluding a and b.
[a,b) means all the real numbers between a and b including a and excluding b.
(a,b] means all the real numbers between a and b excluding a and including b.
Of course, if a or b are ±infinity, then there will be a round bracket because obviously infinity is not included.

That's about as comprehensive of an explanation you can get.