open query 7

#$&*

course MTH 164

If your solution to stated problem does not match the given solution, you should self-critique per instructions at

http://vhcc2.vhcc.edu/dsmith/geninfo/labrynth_created_fall_05/levl1_22/levl2_81/file3_259.htm

.

Your solution, attempt at solution. If you are unable to attempt a solution, give a phrase-by-phrase interpretation of the problem along with a statement of what you do or do not understand about it. This response should be given, based on the work you did in completing the assignment, before you look at the given solution.

Precalculus II

Asst # 7

&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&

Self-critique (if necessary):

------------------------------------------------

Self-critique Rating:

**** Query problem 6.6.12 cot(2`theta/3) = -`sqrt(3)

YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY

Your solution:

confidence rating #$&*:

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

.............................................

Given Solution:

The cotangent function takes value -sqrt(3) when its argument is 5 pi / 6 or 11 pi / 6, as can easily be seen using a labeled unit circle and the definition of the cotangent.

If the argument of the function is coterminal with 5 pi / 6 or 11 pi / 6 we obtain the same value for the cotangent.

So the possible arguments are 5 pi / 6 + 2 pi n or 11 pi / 6 + 2 pi n, where n can be any integer.

The student solution given below is correct for arguments 5 pi / 6 and 11 pi / 6, but does not address possible coterminal arguments.

2`theta/3 = 5pi/6 or 11pi/6

`theta = 5pi/6 * 3/2 or 11pi/6 * 3/2

`theta = 5pi/4 or 11pi/4

.........................................

23:43:44

......!!!!!!!!...................................

&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&

Self-critique (if necessary):

I wasn’t quite sure about this one. I just didn’t understand.

------------------------------------------------

Self-critique Rating:

@&

You start with the question 'cotangent of what is equal to - sqrt(3).

A completely labeled unit circle will tell you that this value of the cotangent occurs for theta = 5 pi / 6 or theta = 11 pi / 6.

The thing that we're taking the cotangent of is 2 theta / 3. So it's 2 theta / 3 that's equal to 5 pi / 6 or to 11 pi / 6.

Setting 2 theta / 3 equal to these values, in turn, we get two values of theta.

*@

**** List all the possible values of 2 `theta / 3 such that the equation is satisfied (the list is infinite; use the ellipsis ... to indicate the continuation of a pattern)

......!!!!!!!!...................................

YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY

Your solution:

5pi/6

11pi/6

17pi/6

235pi/6

29pi/6

35pi/6

41pi/6

confidence rating #$&*:2

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

.............................................

Given Solution:

2`theta/3 = 2/3(5pi/4 + kpi)

when k=0 2/3`theta = 5pi/6

when k=1 2/3`theta = 11pi/6

when k=2 2/3`theta = 17pi/6

when k=3 2/3`theta = 235pi/6

when k=4 2/3`theta = 29pi/6

when k=5 2/3`theta = 35pi/6

when k=6 2/3`theta = 41pi/6

etc ........

when k=n 2/3`theta = 5pi/6 + npi

** 2 `theta / 3 can be 5 `pi / 6 or 5 `pi / 6 + 2 `pi or 5 `pi / 6 + 4 `pi or in general 5 `pi / 6 + 2 n `pi, or it can be

11 `pi / 6 or 11 `pi / 6 + 2 `pi or 11 `pi / 6 + 4 `pi or in general 11 `pi / 6 + 2 n `pi. **

.........................................

23:57:51

......!!!!!!!!...................................

&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&

Self-critique (if necessary):

------------------------------------------------

Self-critique Rating:

**** How many of these values result in `theta values between 0 and 2 `pi?

......!!!!!!!!...................................

23:59:12

YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY

Your solution:

confidence rating #$&*:

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

.............................................

Given Solution:

** If 2 `theta / 3 = 5 `pi / 6 + 2n `pi then multiplying both sides by 3/2 we get

`theta = 5 `pi / 2 + 3 n `pi. Since 3 n `pi > 2 `pi only 5 `pi / 2 is between 0 and 2 `pi.

If 2 `theta / 3 = 11 `pi / 6 + 2n `pi then multiplying both sides by 3/2 we get

`theta = 11 `pi / 2 + 3 n `pi. Since 11 `pi / 2 > 2 `pi this can't lie between 0 and 2 `pi unless n is negative. **

.........................................

&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&

Self-critique (if necessary):

------------------------------------------------

Self-critique Rating:

**** Query problem 6.6.44 solve sin^2(`theta) = 2 cos(`theta) + 2

......!!!!!!!!...................................

14:41:12

YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY

Your solution:

`theta = -pi + 2 `pi k

confidence rating #$&*:

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

.............................................

Given Solution:

** Since sin^2(`theta) = 1 - cos^2(`theta) we have

1 - cos^2(`theta) = 2 cos(`theta) + 2. This equation is a quadratic equation in cos(`theta). To see this rearrange the equation to get

cos^2(`theta) + 2 cos(`theta) + 1 = 0. Now let u = cos(`theta). You get

u^2 + 2 u + 1 = 0. This is a quadratic equation with solution u = -1.

Thus our solution is u = -1, meaning cos(`theta) = -1, so `theta = -pi + 2 `pi k, for any integer k. **

.........................................

14:43:04

......!!!!!!!!...................................

&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&

Self-critique (if necessary):

------------------------------------------------

Self-critique Rating:

**** Query problem 6.6.66 19x + 8 cos(x) = 0

YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY

Your solution:

0.31

confidence rating #$&*:

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

.............................................

Given Solution:

19x+8cos(x)=2 by putting 19x+8 cos(x) in as y sub1 and 2 as y sub 2 we can

trace and find that the closest value for x is approximately (.30).

.........................................

&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&

Self-critique (if necessary):

------------------------------------------------

Self-critique Rating:

"

end document

Self-critique (if necessary):

------------------------------------------------

Self-critique rating:

"

end document

Self-critique (if necessary):

------------------------------------------------

Self-critique rating:

#*&!

&#This looks good. See my notes. Let me know if you have any questions. &#