(115) Homework 8(Due 12/1)

Hi all,

Our quiz is postponed to Dec 1, which is the Thursday after Thanksgiving. Here is a set of problems due on the same day:

6.1: 6, 8, 15, 16, 23

7.1: 7, 8, 16

7.2: 1, 4

9.1: 2, 4, 8, 10, 12, 14, 15, 35,36,38,40

9.3: 1,2,5,6,8,11,12,21,22,24



(115)Review problems

Hi all,

we have our first test on Thursday, Oct 6. The following is a set of review problems that is never due. But you can hand them in for extra credits.

1.2: 6,7,11,18,23,24,31,33,38,43

1.3: 1,3,7,11,22,24,43

2.1: 13,15,19,25,29(Hint: c=a\pi r)

2.2: 5,6,15,31,41

2.3: 15,56

3.1: 2,4,5,14,20,22,26,28,46,54,59,60,63,65(drawing a picture might help)




(115) Summary of lines

Hi all,

Last week we spent some time on lines, and with all the different forms you learned, I think it might be a good time to sum them up a little.

To find a line, you need two pieces of information: the direction of the line, and the position of the line, it doesn’t matter how you get these information. Like making a burger, you need some bread and some patty, it doesn’t matter where you buy the bread and patty.

The position of a line is always given by a point on the line. It might be the y-intercept, or just any generic point (x_1,y_1) on the line.

The direction of a line is given by slope (or undefined, in case the line is vertical). It might be directly given to you, and there are many ways of grabbing this information:

  1. Any two points (x_1,y_1) and (x_2,y_2) on the line gives the slope by \frac{y_2-y_1}{x_2-x_1}
  2. The line is parallel to a line you already know. For example, if your line is parallel to 3x+2y=5, you know your line has slope -\frac{3}{2}, as parallel lines have the same slope.
  3. The line is perpendicular to a line you already know. For example, if your line is perpendicular to 3x+2y=5, you know your line has slope \frac{2}{3}, as perpendicular lines have slopes that multiple to be -1.