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Mathematics 15 Online
OpenStudy (anonymous):

please get me started : Find a set expression that corresponds to the shaded region shown in the Venn diagram below.

OpenStudy (anonymous):

jimthompson5910 (jim_thompson5910):

there are probably infinitely many ways to do this, but one way is to union those 3 regions

jimthompson5910 (jim_thompson5910):

so you need to find expressions for each region

OpenStudy (anonymous):

ok and how do i start that

jimthompson5910 (jim_thompson5910):

the very middle piece (the smallest shaded region) is the result of intersecting the 3 circles

jimthompson5910 (jim_thompson5910):

basically, it's the region common to all 3 circles

OpenStudy (anonymous):

right

jimthompson5910 (jim_thompson5910):

so that region is \[\Large (A \cap B) \cap C\]

jimthompson5910 (jim_thompson5910):

ie, A intersect B intersect C

jimthompson5910 (jim_thompson5910):

now you need to find the other two shaded regions, they are very similar, so that's a bit of good news

OpenStudy (anonymous):

ok i see that

jimthompson5910 (jim_thompson5910):

look at the upper shaded region

OpenStudy (anonymous):

b?

jimthompson5910 (jim_thompson5910):

yes for set B

OpenStudy (anonymous):

ok

jimthompson5910 (jim_thompson5910):

notice how everything is filled in but stuff from sets A or C (ignore the common middle right now)

OpenStudy (anonymous):

yes

jimthompson5910 (jim_thompson5910):

so that region is basically: everything in set B but kick out stuff from set A or C which turns into \[\Large B \cap (A \cup C)'\]

OpenStudy (anonymous):

ok

jimthompson5910 (jim_thompson5910):

you are basically intersecting set B with everything that is in neither A nor C, that gives you that upper shaded region in B

OpenStudy (anonymous):

ok

jimthompson5910 (jim_thompson5910):

do the same for that last shaded region

OpenStudy (anonymous):

A∩(B∪C)′

jimthompson5910 (jim_thompson5910):

good

jimthompson5910 (jim_thompson5910):

now we have the following regions: --------------------------------------------------- \[\Large (A \cap B) \cap C\] which is the smallest shaded region (in the middle) --------------------------------------------------- \[\Large B \cap (A \cup C)'\] the upper shaded region found in set B --------------------------------------------------- \[\Large A \cap (B \cup C)'\] the lower shaded region found in set A

OpenStudy (anonymous):

right

jimthompson5910 (jim_thompson5910):

we then union those regions together to get the final answer

OpenStudy (anonymous):

ok and what does that mean

jimthompson5910 (jim_thompson5910):

let me show you, one sec

OpenStudy (anonymous):

ok thanks

jimthompson5910 (jim_thompson5910):

if you color and label the regions like this

OpenStudy (anonymous):

ok

OpenStudy (anonymous):

and then just label the equations ewith the regions?

OpenStudy (anonymous):

or do we combine them, ?

jimthompson5910 (jim_thompson5910):

then you can say this:

OpenStudy (anonymous):

and thats the answer ?

jimthompson5910 (jim_thompson5910):

then union them to get this

jimthompson5910 (jim_thompson5910):

so your final answer is this

OpenStudy (anonymous):

ok great! thanks so much!!

jimthompson5910 (jim_thompson5910):

me personally, i like the labels and the colors (so you know what's what), but you'll probably have to drop them

OpenStudy (anonymous):

ok great thanks so much!

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