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Chandan Yashraj
3/6/2011 03:04:08 am
In 9.1, how would you solve numbers 43 and 44, where the y coordinate point is neither in radians nor degrees, but just a plain decimal number. I tried solving it using the formula, but didn't get the answer.
Anika Gupta
3/6/2011 03:49:18 am
Yeah i had the same questions as Chandan, I tried the last ones and got them wrong. I also needed help on number 37. for some reason i did something wrong but i can't figure out what.
Chandan Yashraj
3/6/2011 11:00:42 am
Hey Anika,
Chandan Yashraj
3/6/2011 11:01:46 am
Note: read the root3/2's as (root3)/2. Sorry about having no parentheses.
Chandan Yashraj
3/7/2011 10:47:27 am
On number 49 from 9.1...could the y coordinate, which is according to the answers pi/4...so can I write 7pi/4 for this as well? If you know or have an idea about this, please reply. Thanks.
Chandan Yashraj
3/7/2011 10:53:12 am
My bad. The book says you can't do it that way. Just ignore that.
Meghan
3/7/2011 11:48:01 am
How on Earth do you solve 67??? Looking at the answer in the back of the book made it more confusing.
Anika Gupta
3/7/2011 01:38:32 pm
I was doin tonight's homework and i really needed help on problems 53 and 59. could someone help me please?
Kelly Mathesius
3/8/2011 08:54:40 am
For problem 67, you more or less use the same method you used to solve all of the other ones. So you multiply both sides by r to get r^3 = r cos theta. You can replace the r cos theta with x, so you have r^3 = x. So we know r^2 = (x^2 + y^2), but we need r^3. So if bring each side of the r^2 equation up to the 3/2 power we get (r^2)^3/2 = (x^2 + y^2)^3/2. For the left side of the equation, the powers multiply, giving us r^3 = (x^2 + y^2)^3/2. Now, if we substitute this in for r^3 in the first equation, we get (x^2 + y^2)^3/2 = x. Then you just subtract the x over to get (x^2 + y^2)^3/2 – x = 0.
Kelly Mathesius
3/8/2011 09:16:15 am
Let’s see so for problem 53 you have to use a calculator to figure it out. To find r, you use the formula r^2 = x^2 + y^2. So 1.3^2 + 2.1^2 = 6.1. Take the square root of 6.1 and you find that r = 2.47. Then, to find theta, you say tan theta = 2.1/1.3. When you use the calculator, you get 58.24, but since that isn’t in the range (I think, I don’t remember exactly what was in the book!), you add 360, to find that theta = 301.75. Therefore, the polar coordinates are (2.47, 301.76 degrees). For 59, you simply substitute x = r cos theta and y = r sin theta into the equation. You get (r cos theta)^2 = 4 (r sin theta). After squaring and distributing, you get r^2 cos^2 theta = 4r sin theta. Then, you subtract 4r sin theta from each side to set the equation equal to 0, resulting in r^2 cos^2 theta – 4r sin theta = 0.
Anika Gupta
3/9/2011 11:23:12 am
I neeeded help doing problems 43 and 45 on tonights homework. For 43, i got the graph wrong. and for 45, i just had no idea how to figure out the coordinate points or anything.
Meghan irby
3/9/2011 01:34:03 pm
Thanks Kelly! :)
Julianne DiLeo
3/9/2011 02:40:16 pm
In that example at the end of class the other day the graph showed it was symmetrical about the polar axis but when we tested its symmetry it said it wasnt, does anyone know why that is?
Robert Riley
3/12/2011 10:33:34 am
In order to do polars in the
Kelly Mathesius
3/12/2011 11:37:30 am
Julianne, the symmetry tests are kind of inconsistent. The symmetry tests only prove that a graph is symmetrical, not that it isn’t symmetrical. If the test works, then you know the graph is symmetrical somehow. But if it doesn’t work, it doesn’t necessarily mean it isn’t symmetrical, but you just have to plot more points to check. Hope this helps.
Kelly Mathesius
3/12/2011 11:42:55 am
And Robert, no, it doesn’t always have to be in radians. However, when you graph it in degrees, the graph is really stretched out because it is graphed over the course of 360 degrees, which, numerically, is much larger than the 2 pi radians if you graph in radians. Basically, if you want to graph in degrees, you just have to modify the window.
Kelly Mathesius
3/12/2011 12:29:00 pm
For 43, you can determine that it is a rose with 4 petals by looking at the equation and comparing it to the chart on page 582 in the book. I’m horrible at describing stuff, but it should look like a rose with four petals, centered at the origin, with each petal 3 units from the pole. Using the symmetry tests, you know it is symmetrical with respect to the xaxis so I only found points from 0 to pi. For 45, you should get a rose with 3 petals, with each petal reaching to 4 units from the pole. Using the symmetry test, you can determine it is symmetrical about the yaxis, so you only have to find points ranging from 3 pi/2 to pi/2. Then, you simply follow the same process of finding points that you have been using. For example, if we say theta is pi/6, then r = 4 sin (3 (pi/6)). Next: r = 4 sin (3pi/6), r = 4 sin (pi/2), r = 4 sin (1), r = 4. So the coordinate we just found is (4, pi/6). Then you would just plot this point and repeat the process until you can determine the graph.
Melina Moussetis
3/12/2011 02:53:24 pm
on the first section of 9.3 homework does anybody know how to do number 10?
Mrs. J
3/12/2011 03:13:13 pm
@Melina:
Vish Patel
3/13/2011 04:29:01 am
How do you distinguish the difference between the graph with the loop in the middle and the graph without it? And how do you know how many petals there are?
Sivani Aluru
3/13/2011 05:05:06 am
Hey guys. This is mainly for lesson 9.3, but I found this great video (or sets of videos) that explain the complex plane and how to write complex numbers in rectangular form and vice versa. Enjoy! :
Madeline Zehnal
3/13/2011 08:08:07 am
Sivani,
Madeline Zehnal
3/13/2011 08:09:19 am
Vish,
Chandan Yashraj
3/13/2011 08:38:37 am
Maddie,
Julia DiMonte
3/13/2011 08:46:01 am
Madeline, if you are told (6, pi/6) in the form of p= (r, theta) then all you have to do is remember the equations to transform each.
Chandan Yashraj
3/13/2011 08:52:04 am
Sivani, thank you so much for the link...I'm not only using it for math now, but for chem as well ;).
Lexy Neville
3/13/2011 08:57:36 am
How do you do number 22 on 9.3? I don't understand how to solve when you have to find the cosine and sine of pi/10
Julia DiMonte
3/13/2011 09:14:27 am
On the worksheet it says to transform the equation r=2cosx so that it indicates a rotation of pi/2 counterclockwise and a rotation of pi/3 clockwise. How do you do that?
Kayla Simon
3/13/2011 10:22:31 am
I'm confused on problem 25 in 9.3. The answers say that it should be 12(cos40+isin40) but I keep getting 400. Is there a missing zero or am I missing something?
Justin Temple
3/13/2011 10:39:14 am
Kayla,
Kelly Mathesius
3/13/2011 11:29:28 am
Julia,
Kelly Mathesius
3/13/2011 11:36:39 am
Lexy,
Chandan Yashraj
3/13/2011 12:01:44 pm
I don't get how you would do the transformation for part 1b on the polar worksheet. I get the pi/2 one, but how would you know which coordinates will work for the pi/3 one...?
Beatrice Koka!
3/13/2011 01:16:11 pm
I'm a little confused on #25 in section 9.3, i understand how to do:
Alex Tazic
3/13/2011 01:48:17 pm
its not really subtracting 360 because 400 is the same angle as 40 they are just using it in terms that we can use on the unit circle
Alex Tazic
3/13/2011 02:01:59 pm
and for chandan i think you would just put r = 2cos(theta  PI/3)
Nithya Sridhar
3/13/2011 02:32:48 pm
I was a little confused about the "More Polar Graphing" Worksheet
Alex Masiak
3/14/2011 12:16:51 pm
Vish (way up there),
Chandan Yashraj
3/14/2011 01:00:19 pm
For the PISA essay, does anyone know if we need to make an outline? If you look at the sheet under the College Test Prep page, it says to on the sheet, but I thought that was only pertaining to the class that has the assignment...(<?)
Jamez Hunter  Phd in Love
3/14/2011 02:01:28 pm
Chandan! Hi!
maddie
3/15/2011 08:24:49 am
are we supposed to watch the video to write the paper?
maddie
3/15/2011 08:49:53 am
i'm really confused about this writing assignment. Can someone explain it?
Chandan Yashraj
3/15/2011 09:07:47 am
Maddie,
Sohaila M
3/15/2011 11:27:52 am
Im a little confused on how to do problem #40 in 9.3...if anyone could explain it, thatd be great!
Sohaila M
3/15/2011 11:32:34 am
oh and Beatrice, for #25 they put the answer as 12 [cos 40 + isin 40]. They do subtract 360, but when you think about it, the sin and cos of 40 degrees is actually the same as 400 degrees, because they are just going around the unit circle again.
Sohaila M
3/15/2011 11:33:03 am
oh. nvm. alex already answered that..
Sejzelle ErastusObilo
3/15/2011 01:04:26 pm
Does anyone know how to do number 43 from 9.3? Thanks!
Chinar R.
3/15/2011 01:39:09 pm
Hey Sejzelle, this is what I did for that one...
Chinar R.
3/15/2011 01:39:48 pm
So that means you have three answers for 43, by the way.
Shivani D.
3/15/2011 02:02:59 pm
For the writing assignment, do we have to cite sources within the essay? and how long does it have to be?
Jacob Hayes
3/15/2011 02:14:39 pm
Chinar, 360/3 = 120.
Julianne DiLeo
3/15/2011 03:11:33 pm
Shivani,i think if you used sources then you will need to cite it, she did say MLA format. Although it was supposed to be like a act writing prompt so im not sure if you really needed to use outside information... i dont know i could be wrong. it probably should be four to five paragraphs as well. i have a question though, do we turn it in tomorrow or email it to her tonight????
BFrank
3/15/2011 03:33:38 pm
I know she said it has to be 5 paragraphs, and yes i do believe that we have to email it to her tonight because she is going to check it into turnitin.com for legibility reasons.
Chandan Yashraj
3/15/2011 04:21:40 pm
Yes, that is correct. She said you have to turn in your soft copy into her via email, and she'll take care of the rest with the turnitin stuff.
Chinarzard
3/15/2011 06:03:10 pm
Jacob,
Chandan Yashraj
3/16/2011 10:39:27 am
On number 9 in the review section, why can't the coordinate point (2,pi/2), which is the answer in the back of the book for one of the answers, be written as:
Chandan Yashraj
3/16/2011 10:50:52 am
How would you solve number 11 from the review section?
Chandan, you are correct in saying that there are several ways to write each polar coordinate. However, reading the directions will yield the following:
Chandan Yashraj
3/16/2011 12:20:02 pm
But Kyle, isn't r the x coordinate...the y coordinate is what I am concerned about. I got the negative and positive x coordinate, but is 3pi/2 or pi/2 right for the y coordinate?
Sean Curran
3/16/2011 02:33:18 pm
yea, i would think so, since they are the same point. i guess there would be four answers.
Jacob Hayes
3/16/2011 02:35:49 pm
For problem 41 of the review, this is vectors correct? I dont think we need to know this for the test friday since the test is over 9.19.3 but can anyone just confirm or deny this for me? Thanks
Shivani D
3/16/2011 03:00:04 pm
Hi Jacob! We do need to know that, since it is in section 9.3. It is part of Demoviare's theorem:)
Shivani D
3/16/2011 03:07:48 pm
Hey! for number 11 on the review, are we supposed to use a calculator to figure it out? isn't that the only way, since the unit circle does not tell us what angle has a tangent of 3/4?
Ayo Adewole
3/16/2011 03:15:53 pm
hey shivani, for problems like
Vish Patel
3/17/2011 08:56:22 am
I don't understand how to do number 15 on the review. I keep trying to simplify it but i can't get it to a point where i can make it polar coordinates. How do i get it into an equation where i can substitute r for (x^2)+(y^2) or
Chandan Yashraj
3/17/2011 09:53:07 am
Vish, you know that for this problem you have to do the OPPOSITE of what you mean...? Your goal is to go from terms of x and y to terms of an sin/cos/tan, etc. Are you referring to another problem?
Chandan Yashraj
3/17/2011 10:07:16 am
In section 9.1 how would you do number 43 and 44...I am very confused on those.
Eric Cheng
3/17/2011 10:15:03 am
Chandan, for those, you just do the same thing even though it is not in theta form.
maddie strick
3/17/2011 10:42:17 am
can someone explain number 40 from 9.3 and number 49 from the review?
ch
3/17/2011 10:48:21 am
Chandan Yashraj
3/17/2011 10:49:29 am
Ok, wow, sorry about the ch above.
Chandan Yashraj
3/17/2011 11:05:31 am
Maddie:
maddie strick
3/17/2011 11:08:14 am
can you explain how to convert root3i to polar form...thanks
Sohaila
3/17/2011 11:08:14 am
Hey chandan, for problems that are in decmal form u put it as radians, because if u were to calculate out a fraction with pi you would get a decimal. You would only use degrees if the questions asked you to find the sin,cos,tan etc of a certain degree measure.
maddie
3/17/2011 11:17:54 am
ok nevermind i get how to do 40...but i'm still stuck on 49
Chandan Yashraj
3/17/2011 11:22:07 am
In 9.3, when you are trying to solve for Complex Roots...how do you know what k equals? In example 6, how does k go until 2 (including 0 and 1), and not 3...? We went over this in the last 2 minutes of class so I didn't catch this part.
sohaila
3/17/2011 11:25:14 am
for #15, 3/17/2011 11:27:48 am
@maddie
maddie
3/17/2011 11:32:12 am
Thanks! what about 49 from 9.3? 3/17/2011 11:32:17 am
@Chandan Yashraj
Muhammed Alikhan
3/17/2011 11:33:40 am
@chandan
Muhammed Alikhan
3/17/2011 11:42:00 am
@maddie
Alex tazic
3/17/2011 11:57:13 am
When converting back to polars and you get like cos theta is 5/13 how do u find that angle without a calculator
Meghan Irby
3/17/2011 12:09:26 pm
Alex  I don't believe you can find it without a calculator because it comes out to some crazy angle not on the unit circle. I assume we wouldn't have noncalculator ones like that on the test :) hopefully
Chandan Yashraj
3/17/2011 12:10:37 pm
Thanks Ashwin and Muhammed. That cleared up a lot of stuff.
Chandan Yashraj
3/17/2011 12:12:57 pm
@ Meghan
Kayla Simon
3/17/2011 12:13:50 pm
Meghan, since you substitute rcostheta for x and rsintheta for y, the r's cancel out when you do y/x, and you subtract it to the other side.
sohaila M
3/17/2011 12:43:06 pm
yea on number 12 on the review i understand how they got 13 as r, but i am a little confused with how they got 1.96 as the theta, for one of the answers.
BfRaNk
3/17/2011 12:45:58 pm
Sohaila (kinda way up there) for number 43 I believe you have to use Demoivre's theorem but im still having difficulty with it. Can anyone help?
Wesley Lai
3/17/2011 12:50:15 pm
im having trouble graphing complex roots on the calculator, ive looked at the steps on page 592 but its still confusing, any advice?
Alex Masiak
3/17/2011 01:06:00 pm
@bfrank
Shivani D.
3/17/2011 01:11:48 pm
Hey! i'm really confused about how to solve 12 on the review....i keep getting 1.17 for theta, can someone help me out?
Christian Noblett
3/17/2011 01:24:49 pm
Hey BfRaNk for number 43 you do use Demoivre's theorem.
Shivani D.
3/17/2011 01:43:20 pm
Hey I had another question about 9.1, number 49. For my answer, I got root2, 7pi/4. The book says it's root2,pi/4. Does it matter whether it's 7pi/4 or pi/4?
JacJames Hayes
3/17/2011 01:45:28 pm
No it wouldnt, both are correct. Although i'd say 7pi/4 would be the safer answer as most answers are contained to between 0 and 2pi
Chandan Yashraj
3/17/2011 01:49:03 pm
@wesley
Shivani D.
3/17/2011 01:52:02 pm
oh nevermind jacob! since, the domain of tangent is from pi/2 to pi/2.
Chandan Yashraj
3/17/2011 01:52:40 pm
@Shivani
Jacob Hayes
3/17/2011 01:52:59 pm
Setting mode to Polar lets you use polar equations but i dont think that'd help with imaginary numbers... Like Chandan said just graph with x as real and y as imaginary.
Chandan Yashraj
3/17/2011 01:58:21 pm
Jacob, I just checked setting to polar and graphing, but that doesn't change anything. So yea, just stick with setting the axes to respective settings and graph by hand.
Chandan Yashraj
3/17/2011 02:39:15 pm
For the graphing of the polar graphs, how do you know if the spiral continues forever or stops at a certain point...?
Justin Temple
3/17/2011 03:03:07 pm
Chandan,
Chammy
3/17/2011 03:04:20 pm
Chandan i think that all graphs on the calculator stop the spirals at a certain point. Because if you plug in the equation shown in example 13 on page 581 into your calculator, it stops at the polar axis but the picture shows it continuing. I'm guessing that they'res just a certain range that the calculator limits the equation to (which is weird because if you look at the table, it continues forever).
Shivani D.
3/17/2011 03:50:14 pm
Hey!! I have one last question for 56 on the review. for my answers, i got 2, 2, 2i, 2i, but the actual answers say root 2, root 2i, etc...can someone explain this to me?
Sejzelle ErastusObilo
3/17/2011 04:10:07 pm
Hey Shivani, how did you get those answers?
Shivani D.
3/17/2011 04:15:35 pm
Hi Sejzelle!
Muhammed Alikhan
3/17/2011 04:16:51 pm
Shivani, for 56, it would be asking for the fourth roots o 16, so these would be the roots of all your answers since you only went up to the third roots. (4i is the 2nd root, the root of that is the 3rd, and the root of that is the fourth).
Sejzelle ErastusObilo
3/17/2011 04:34:38 pm
Thanks, Shivani, and where did the 4 come from?
Sejzelle ErastusObilo
3/17/2011 05:04:19 pm
Sohaila...really high up Comments are closed.

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