Question

Is there a way to graph this in calc ?
r=2+4cos theta

Answer 1

@satellite73 here :D

Answer 2

on a calculator? dunno, but you can certainly do it here
http://www.wolframalpha.com/input/?i=r%3D2%2B4cos%28theta%29

Answer 3

you know how to do it manually? cuz i need to know for a test :O

Answer 4

@dpaInc help! :|

Answer 5

what kind of calculator do you have?

Answer 6

TI-84 Plus

Answer 7

then that's easy... just get in polar mode...

Answer 8

do you know how?

Answer 9

everybody keep saying polar mode but idk what polar mode is, only know Trig mode

Answer 10

i mean your calculator... do you have it with you?

Answer 11

yes

Answer 12

there's a mode button on it.... press it...

Answer 13

ok

Answer 14

and choose polar

Answer 15

i only see POL

Answer 16

that's it... you need to have that highlighted.... by moving the cursor with the arrow keys. then press enter.

Answer 17

ok

Answer 18

now press [2nd] [QUIT] to get back to home screen

Answer 19

ok

Answer 20

now press [y=] to enter your equation....

Answer 21

just enter it in like that? what about the theta? enter that too ?

Answer 22

when your in polar mode, the button [x,T,theta,n] will choose theta for you.. it all depends on which mode you're on.

Answer 23

ok then what else?

Answer 24

that's it.... press graph and your calc should show your graph.

Answer 25

i dont see anything =.=

Answer 26

im in standard zoom btw

Answer 27

one more thing.... you need to have your calculator in radian mode also...

Answer 28

oh wow =.=

Answer 29

now do you see it?

Answer 30

yes! i see it, but how do i know the points?

Answer 31

you can still do the regular things you do when you're in regular mode like trace, table, etc....

Answer 32

oh ok!

Answer 33

in fact, press [table]

Answer 34

ok

Answer 35

do you see the theta, r table?

Answer 36

yes

Answer 37

don't forget... the theta is in radians and NOT degrees

Answer 38

ok

Answer 39

those are your "points" like the "x,y" in the regular mode.

Answer 40

alot of decimals :|

Answer 41

hopefully he won't give any trick answers on the test :|

Answer 42

otherwise if he just give this picture then im good lol

Answer 43

hang on...
press [window]

Answer 44

uh huh

Answer 45

you have to be careful with polar graphs ...

Answer 46

are you in the [window] screen?

Answer 47

yes

Answer 48

sometimes your whole graph will not show depending on theta..
for example, make THETAmax = pi instead of THETAmax = 2*pi

Answer 49

now graph

Answer 50

do you see the resulting graph?

Answer 51

i think i only see half of the graph before

Answer 52

right... because you also need to consider the DOMAIN of your equation...

Answer 53

I'm just saying that your calculator might not show what you want if your THETAmin/THETAmax is not set properly... so be careful with that.

Answer 54

lol it turn weirder and weirder lolo

Answer 55

wait how do i go back to the original ?

Answer 56

you mean the graph? it shouldn't change

Answer 57

standard zoom

Answer 58

oh lol =.=

Answer 59

does your teacher make you do plots of (r, theta) ?

Answer 60

you mean plot the points manually ?

Answer 61

yes...

Answer 62

dont think so, but when i look at the answer's graph i do see points though

Answer 63

that can easily obtained by the table...

Answer 64

we never did this in class, he just include this in the final to kill us :| i hate that man lol

Answer 65

hmm... How do you know that I'm not him?

Answer 66

uh oh o_0

Answer 67

kidding!!!

Answer 68

lmao u gave me a mini heart attack =.=

Answer 69

that was great...
anyway, you can get the easy theta points easily also... press [2nd][table set]

Answer 70

ok

Answer 71

see the triangleTBl = 1 ???

Answer 72

yeah

Answer 73

and TblStart = 1 ???

Answer 74

tbstart=0 , should i change it to 1 ?

Answer 75

change them to this...
TblStart = 0
triangleTbl = pi/6

Answer 76

what else?

Answer 77

hmm when i look at the answer in my book, it show graph and points, but the points have number then degrees next to it :|

Answer 78

that's it.... now press [2nd][table]

if your teacher asks you to plot several points, you can use this table that gives the decimal equivalents of theta incrementing by pi/6

Answer 79

degrees?

Answer 80

you wanna see the picture? i can upload it here

Answer 81

sure.

Answer 82

can you see it?

Answer 83

ok, no problem..

Answer 84

you still have your calculator in front of you?

Answer 85

yes

Answer 86

press [MODE] -> [degree]

Answer 87

press enter

Answer 88

ok just change it back to degree i guess

Answer 89

yeah, sorry

Answer 90

but that won't show me the graph

Answer 91

i know.... we need to change the window settings...

Answer 92

ok

Answer 93

2nd+window ?

Answer 94

right...
thetamin = 0
thetamax = 360

Answer 95

thetastep = 30

these numbers are all in degrees

Answer 96

ok then what else?