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,

**π**^{c}/10,

**π**^{c}/5, (3

**π**^{c})/10, (2

**π**^{c})/5,

**π**^{c}/2, (3

**π**^{c})/5, (7

**π**^{c})/10, (4

**π**^{c})/5, (9

**π**^{c})/10, and

** π**^{c}
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,

0.13

**π**^{c}, and 0.86

**π**^{c}, 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 = (2

**π**^{c})/15 and x = (13

**π**^{c})/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

** π**^{c}/10 for 2 cm on the X axis and 2cm for 1 unit on the Y axis.

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