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Mathematics 21 Online
OpenStudy (anonymous):

Please help! I always give medals and become a fan! Which features are present in this polar graph? (more than one answer.) PICTURE ADDED BELOW a. no symmetry b. symmetry about the line theta = pi/2 c. symmetry about the pole (0,0) d. symmetry about the polar axis theta=0.

OpenStudy (anonymous):

jimthompson5910 (jim_thompson5910):

were you able to get anywhere?

OpenStudy (anonymous):

no not really! I'm not really sure how to go about the problem

jimthompson5910 (jim_thompson5910):

I'm assuming you've found function inverses before in the past?

OpenStudy (anonymous):

uhm it sounds familiar... kind of

jimthompson5910 (jim_thompson5910):

actually no that won't work here, nevermind that thought

jimthompson5910 (jim_thompson5910):

theta = pi/2 is the angle that's at 90 degrees, so if you were to fold the figure over the y axis, would it match up with itself?

OpenStudy (anonymous):

haha okay! (:

OpenStudy (anonymous):

no it wouldn't

jimthompson5910 (jim_thompson5910):

the y axis is the vertical axis

jimthompson5910 (jim_thompson5910):

you sure?

OpenStudy (anonymous):

wait so it would then

jimthompson5910 (jim_thompson5910):

yes it would, try drawing it out on paper and folding it up yourself

jimthompson5910 (jim_thompson5910):

you'll see things match up perfectly (or close enough depending on how accurately it's drawn)

jimthompson5910 (jim_thompson5910):

so there is symmetry with respect to the line theta = pi/2

jimthompson5910 (jim_thompson5910):

how about with theta = 0?

OpenStudy (anonymous):

okay so I know for sure that a. is wrong and b. is right. :)

OpenStudy (anonymous):

how would I find that out?

jimthompson5910 (jim_thompson5910):

yes a) is out because b) is true

jimthompson5910 (jim_thompson5910):

well fold the figure over the x axis and see if things line up

OpenStudy (anonymous):

so this would be folding it horizontally, correct? so it wouldn't line up

jimthompson5910 (jim_thompson5910):

yep it doesn't line up

jimthompson5910 (jim_thompson5910):

so there is no symmetry over the line theta = 0

jimthompson5910 (jim_thompson5910):

how about symmetry with respect to the pole (0,0)

OpenStudy (anonymous):

how do I do that?

jimthompson5910 (jim_thompson5910):

one sec

jimthompson5910 (jim_thompson5910):

a polar graph is symmetric with respect to the pole (0,0) if you can rotate the figure 180 degrees and it will line up with itself

jimthompson5910 (jim_thompson5910):

so when you rotate the figure 180 degrees, does it line up with itself?

OpenStudy (anonymous):

yes

jimthompson5910 (jim_thompson5910):

look at the bottom blade if you rotated it 180 degrees, does that bottom blade line up with either of the top blades?

OpenStudy (anonymous):

no

jimthompson5910 (jim_thompson5910):

so it's not symmetrical with respect to the pole (0,0)

OpenStudy (anonymous):

okay thank you sooooo much!!

jimthompson5910 (jim_thompson5910):

you're welcome

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