richiesmasher
Junior Member
- Joined
- Dec 15, 2017
- Messages
- 111
Hello, I have a function y=3Cos2x
Now I have a graph which I plotted, it makes a nice curve.
Here are the x Values: 0, πc/10, πc/5, (3πc)/10, (2πc)/5, πc/2, (3πc)/5, (7πc)/10, (4πc)/5, (9πc)/10, and πc
The corresponding Y values after running through the function in order from the first x value are: 3.00, 2.43, 0.93, -0.93, -2.43, -3.00, -2.43, -0.93, 0.93, 2.43, 3.00
Now the question asked for the solutions of : 3Cos2x=2.0
My first thought was to look at my graph and see where the line y=2.0 intercepts the curve and found the corresponding x coordinates, I did and obtained,
0.13πc, and 0.86πc, which when you multiply by 180 to turn into degrees, I get 23.4 degrees, and 154.8 degrees, which I'm fairly sure is correct
as my book has x = 24 degrees, and x = 156 degrees, so I'm guessing that my graph was just a bit to the left and it's human error.
However, they also have x = (2πc)/15 and x = (13πc)/15
Am I missing something? how did they get that? Did I have to use the function and solve it?
The scale on my graph is πc/10 for 2 cm on the X axis and 2cm for 1 unit on the Y axis.
Now I have a graph which I plotted, it makes a nice curve.
Here are the x Values: 0, πc/10, πc/5, (3πc)/10, (2πc)/5, πc/2, (3πc)/5, (7πc)/10, (4πc)/5, (9πc)/10, and πc
The corresponding Y values after running through the function in order from the first x value are: 3.00, 2.43, 0.93, -0.93, -2.43, -3.00, -2.43, -0.93, 0.93, 2.43, 3.00
Now the question asked for the solutions of : 3Cos2x=2.0
My first thought was to look at my graph and see where the line y=2.0 intercepts the curve and found the corresponding x coordinates, I did and obtained,
0.13πc, and 0.86πc, which when you multiply by 180 to turn into degrees, I get 23.4 degrees, and 154.8 degrees, which I'm fairly sure is correct
as my book has x = 24 degrees, and x = 156 degrees, so I'm guessing that my graph was just a bit to the left and it's human error.
However, they also have x = (2πc)/15 and x = (13πc)/15
Am I missing something? how did they get that? Did I have to use the function and solve it?
The scale on my graph is πc/10 for 2 cm on the X axis and 2cm for 1 unit on the Y axis.
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