## moongazer 3 years ago What is the meaning of "or" , "and" in math?

1. moongazer

and what do you call those?

2. UnkleRhaukus

a or b (inclusive)\[a\vee b\] a and b \[a\wedge b\]

3. UnkleRhaukus

|dw:1348403720368:dw|

4. UnkleRhaukus

|dw:1348403767690:dw|

5. UnkleRhaukus

|dw:1348403820405:dw|

6. moongazer

what do you call those "and" "or"

7. UnkleRhaukus

Conjunction \wedge \(\wedge\) Disjunction \vee \(\vee\)

8. moongazer

thanks, can you help in finding a domain of a function?

9. UnkleRhaukus

Negation \neg \(\neg\) |dw:1348404218012:dw| \[\neg C\]

10. UnkleRhaukus

11. moongazer

|dw:1348405394804:dw|

12. UnkleRhaukus

factorise the numerator and denominator

13. moongazer

btw, "or" is like the union of the set and "and" is like the intersection of a set. Is that correct?

14. moongazer

|dw:1348405630353:dw|

15. moongazer

@UnkleRhaukus

16. UnkleRhaukus

"or" is like union "and" is like intersection kinda but they are used for slightly different things, i think the logic symbols are used for points, where as the set symbols are used for sets of points

17. UnkleRhaukus

what is the only number that dosent make sense in a denominator ? , what are two point values for x that would make your function undefined ?, exclude these from your domain

18. moongazer

{x|x>2 and x>3 and x>=5 and x>=4} is this correct?

19. moongazer

@UnkleRhaukus

20. UnkleRhaukus

i get \[\{x|((x≠2)\wedge (x≠3))\}\]

21. UnkleRhaukus

hmm im not right though

22. moongazer

The answer in my notebook says: dom K: {x|x<2 or 3<x<=4 or x>=5} I only copied that from my classmate because I was absent when my teacher discussed this. so I don't know how they got that

23. UnkleRhaukus

there is a strange discontinuity where 4<x<5

24. moongazer

my notes also says that "use the number line to graph the values for which the function is defined.

25. moongazer

that is for finding the domain.

26. moongazer

@UnkleRhaukus

27. UnkleRhaukus

well x is defined from -∞ to 2 , at 2 this is a discontinuity, the from 2 to 4 defined, then discontinuity from 4 to 5 then defined again from 5 to ∞