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April 8th, 2009, 06:35 PM   #1
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Graphing sin

Is this done right? The main question is line 5, i must have done someting wrong in line above but dont knwo what. Any help is appreciated. Thanks
y=2-2sec(x-pi/5)
0<= x-pi/5 <= 2pi
2pi/1+pi/5 = 11pi/5?

pi/5 <= x <= 11pi/5

Make table:
pi/5+11pi/5 = (12pi/5)2 = 6pi/5? pi/5+6pi/5 = (7pi/5)/2 = 7pi/10? 6pi/5+11pi/5 = (17pi/5)2 = 17pi/10? Line 1 table
7pi/10 - pi/5=pi/2? 6pi/5 - pi/5 = pi? 17pi/10 - pi/5 = 3pi/2? 11pi/5 - pi/5 = 2pi? Line 2 table
sec(pi/2) = pi/2? sec(pi) = 0? sec(3pi/2) = -2pi? sec(2pi) = 0 Line 3 table
-2(pi/2) = -pi? -2(0) = 0 -2(-2pi) = 4pi? Line 4 table
2-0 = -2? 2 - pi = ? 2 - 0 = -2? 2 - 4pi = ? 2 - 0 = -2 Line 5 table
x | pi/5 | 7pi/10 | 6pi/5 | 17pi/10 | 11pi/5 |
x-pi/5 | 0 | pi/2 | pi | 3pi/2 | 2pi |
sec(x-pi/5) | 0 | pi/2 | 0 | -2pi | 0 |
-2sec(x-pi/5) | 0 | -pi | 0 | 4pi | 0 |
2-2sec(x-pi/5) | -2 | ? | -2 | ? | -2 |
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April 8th, 2009, 07:10 PM   #2
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As you haven't stated what you're trying to accomplish, it's impossible to assess what you've done (other than to observe that some parts don't seem to make any sense).
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April 8th, 2009, 07:17 PM   #3
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Re: Graphing sin

im trying to find my points with the table at the bottom to graph that equation. I need to graph y=2-2sec(x-pi/5). it looks a little hectic, but didnt know how else to show my work. The formatting didnt come out how i wanted it to. the last 5 lines are the tablei was taught to do. the lines above that are how i come up with points that are i the table. The top row is the x poitn, the last row is the y points. I dont know how else to show it whree you can read it better.
on top row of table the x row, is max and min or wave, the rigth most and left most respectively. take the averge of those to find the center point of table, then take average of first and third to second, then average of third and last to find fourth. then move to second row, x-pi/5, take the first number of first row, the x number, and subtract pi/5. do that down the row to fill in blanks,
repeat steps till get to last row which is the y points. Then graph using x and y points.
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April 9th, 2009, 04:42 AM   #4
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Surely you can check any individual values of the function (except that sec(pi/2) is undefined) using a calculator. You could also see the graph using a graphic calculator.
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