Lecture Notes 8/27/18 through 8/31/18 (complete)

Lecture Notes 8/27/18

Lecture Notes 8/29/18

Lecture Notes 8/31/18

10.2#2

Good afternoon Dr. Taylor,

I have a question regarding Problem 2 on the Section 10.2 homework. The question asks me to find a 3D unit vector in the same direction as the 3D vector a = <5,2,-1>. I went through the motions for finding a unit vector (first finding the length with the Pythagorean theorem, then dividing each vector component by the length) and got 0.913i+0.365j-0.183k as my unit vector in the same direction. I double checked the length to make sure it was 1 by doing Pythag again, and the length was 1. However, WeBWorK is saying that I'm wrong, and after a bit of Googling to find similar problems, it looks like I have done the work correctly. My question is, why am I wrong?

Thank you, and sorry if this email is a little long-winded for a single question.

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No apologies necessary, you did exactly what you should do.  It looks to me like you have the right answer, so I'm not sure what the problem with webwork is. There is a little button down at the bottom of the page that says "Email Instructor"; if you click on that it will send me a copy of your webwork page and I can usually spot  what is going wrong.

10.3#7

Dr. Taylor, I have been racking my brain for 30 minutes on this problem, and I don't see any possible answer other than the one I have given. I used the projection formula we learned in class and even went through the problem with a fellow classmate who agreed that my work seemed correct. Thank you for your time.

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well, you have the vector projection correct.  The scalar projection is b.a^  =  b.a/||a|| which is 
             [(-1)x3 + 4x(-3) + (-1)x(-4)]/√(3^2 + (-3)^2 + (-4)^2)  = [-11]/√34

So, your issue is you're using b.a/||a||^2 (and maybe also that you didn't look at the textbook?)

10.2#3

I am not sure what the problem is looking for I found the components to the unit vector in the opposite direction but I am trying to find an angle. I am just unclear on what it is asking.

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well, it's asking basically for just what you've given it: 
1) a vector point in the opposite direction from <4,4>--it will have two equal components that will both be negative, and 
2) a unit vector, that is a vector for which the squares of the components add up to 1.

Lecture Notes 8/20/18 through 8/24/18 (completed)

Lecture Notes 8/20/18

Lecture Notes 8/22/18

Lecture Notes 8/24/18

Due date for section 10.1 postponed for 24 hours

Due to the number of questions about section 10.1 hw, I've pushed the due date back to tomorrow night.

Want to make some money?

So maybe practice some calculus?

(reproduced with permission https://licensing.andrewsmcmeel.com/classroom-usage)

Problem 10.1#2 and #3 [[and how (not) to ask a question]]

This problem stated that I've gotten the right answer wrong due to spacing.

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I've entered in a correct answer to the problem, but the system changed my answer to an un-simplify version of the answer.

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Problem 2:  No. It's not the right answer, and that's not what the problem stated. If you clicked the "Check Answers" button, here is what it said:

It's complaining that your answer *isn't* a number. In fact you *did* give it a list of numbers. The problem as stated is asking for a *distance*, and a distance is a number not a list of numbers. Your answer is the wrong kind of *thing* to be the right answer.

Problem 3: No again, but at least your answer is the right kind of thing this time. You don't understand what the problem is asking, and as a result you're complicating what should be an super easy thing to do.

THE MORE MAJOR PROBLEMS
1) You haven't even asked me a question. I'm not exactly sure what you mean to say, but it sounds like you are complaining about the unfairness of the software, which is a fruitless endeavor because the software doesn't care.
2) You haven't demonstrated to me that you did your own diligence. The textbook covers this material in some detail. I can kind-of guess what you were thinking from the kind of wrong answers you gave, but you'll learn better if you yourself state what you are thinking. You should tell me what page(s) of that material you tried to apply, or what techniques you used and why you thought you should use them.  Also, I need to know that you bothered to do your part before I can effectively teach you,  and you'll learn more effectively when I can show you what specific tool you misapplied or misunderstood.

Want to try again?

section 10.1#4

If I'm not mistaken, the first equation in this problem represents a line, not a plane. Do I leave it blank? There's no option that describes a line.

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Well, what you say would be true in the right situation, except that you've mistaken the situation. Notice that clause about "equations represent in R^3"? So if you need three variables needed to describe points in R^3, say x, y, z, and you've got a single equation that contains only two of those variables, does that equation constrain the value of the third variable at all?

Office Hours posted.

Just over half the class, sixty two people, bothered to respond to the office poll.  Given that I'm supposed to have an hour of office hours for every hour in class, it looks like we can accommodate an opportunity to attend a scheduled office hour for a maximum number of those people (fifty of them) if we follow the following schedule:

Mondays 10:30-11:30AM and 2:45-3:45 PM,
Fridays 3:45-4:45 PM

Of course I remain available at other times by appointment. 

Worried about your grade?

Yeah. I've been here. You don't want to be here.

Welcome to MAT267, and some useful information

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3) The first homework assignment is sections 10.1 and 10.2, which due on Friday August 31 at 11:59 PM.