assignment 11open query

course Mth 173

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.

011. `query 11

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Question: `q problem 1.7.6 (was 1.11.4) continuity of x / (x^2+2) on (-2,2)is the function continuous on the given interval and if so, why?

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Your solution:

This function is continuous because it is impossible for the denominator to become 0 ever so there for it can not be zero on this interval so it must be continuous.

confidence rating #$&*

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3

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Given Solution:


 ** The denominator would never be 0, since x^2 must always be positive. So you could never have division by zero, and the function is therefore defined for every value of x. The function also has a smooth graph on this interval and is therefore continuous.

The same is true of the correct Problem 4, which is 1 / `sqrt(2x-5) on [3,4]. On this interval 2x-5 ranges continuously from 2*3-5=1 to 2*4-5=3, so the denominator ranges continuously from 1 to `sqrt(3) and the function itself ranges continuously from 1 / 1 to 1 / `sqrt(3). **

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Self-critique (if necessary):

ok

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Self-critique rating #$&*

3

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Question: `q query problem 1.7.24 5th; 1.7.20 4th (was 1.11.9) continuity of sin(x) / x, x<>0; 1/2 for x = 0. Where is the function continuous and where is it not continuous?

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Your solution:

For sin theta/theta theta=0

Sin(0)/0= undefined so it is non-continuous.

For ½ for theta =0

I am not sure what to do in this case because the function does not incorporate theta so would it not just be a answer of .5???????

It doesn't matter what you call the variable.

sin(theta) / theta, theta <> 0; value 1/2 for theta = 0

would have an otherwise identical solution.

confidence rating #$&*

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1

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Given Solution:


 ** Division by zero is not defined, so sin(x) / x cannot exist at x = 0. The function is, however, not defined at x = 0 by sin(x) / x; the definition says that at x = 0, the function is equal to 1/2.

It remains to see what happens to sin(x) / x as x approaches zero. Does the function approach its defined value 1/2, in which case the value of the function at x = 0 would equal its limiting value x = 0 and the function would be continuous; does it approach some other number, in which case the limiting value and the function value at x = 0 would not the equal and the function would not be continuous; or does the limit at x = 0 perhaps not exist, in which case we could not have continuity.

Substituting small nonzero values of x into sin(x) / x will yield results close to 1, and the closer x gets to 0 the closer the result gets to 1. So we expect that the limiting value of the function at x = 0 is 1, not 1/2. It follows that the function is not continuous. **

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Self-critique (if necessary):

I am confused on the second part of this problem and how to do this without the theta being incorporated into the problem?????

You don't have to call the variable theta in order to talk about the sine function. See also my note above.

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Self-critique rating #$&*

1

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Question: `q Query problem

Find lim (cos h - 1 ) / h, h -> 0.

What is the limit and how did you get it?

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Your solution:

I can see from the graph of this function that the limit is 0. I can also sub various values in but I will never reach zero.

confidence rating #$&*

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Given Solution:


 ** For h = .1, .01, .001 the values of (cos(h)-1 ) / h are -0.04995834722, -0.004999958472, -0.0005. The limit is zero. **

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Self-critique (if necessary):

ok

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Self-critique rating #$&*

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Question: `q Query Add comments on any surprises or insights you experienced as a result of this assignment.

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Self-critique (if necessary):

I have a fairly good idea of what is going on but I want to make sure I can explain it in my own words. The limit is the value that approached by a function but does not ever equal the function example being sinx/x I can see on the graph that the graph is approaching 1 but never makes it there, to further validate this I can solve the function sinx/x at point .1 to get .998334 at point .01 to get .999983334 at point .001 to get .99999998333 eventually this does make it to one but I am all but sure it is because my calculator eventually rounds the value to 1. Is my interpretation of the idea and process of this concept correct???????

Your statements here are all correct, and you make the point very well.

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Self-critique rating #$&*

STUDENT QUESTION:

Is the limit also where the function becomes discontinuous?

INSTRUCTOR RESPONSE:

A function is continuous at a certain x value if, as you approach that x value, the limiting value of the function is equal to its value at the point.

This is equivalent to the following two conditions:

If the limiting value of a function y = f(x), as you approach a certain x value, doesn't equal the value of the function, then the function is not continuous.

If the function doesn't have a limit at a certain x value, then the function is not continuous at that x value.

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

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