Question

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Answer 1

So the question is 2cosx + 1 = 0
Rearrange to get\[2cosx = -1\]\[cosx = -1/2\]
Now we can look at a picture of cosx http://www.dplot.com/functions/cos.png
or simply use inverse cos (arcos) to findthe result

Answer 2

Does that make sense so far?

Answer 3

I understand everything up until the chart...

Answer 4

Well the chart is not really necessary but it might help your understanding to think of cos as a curve that we can read off. In this case we want to know when cosx = -1/2.

If you look at the y axis and go to -1 and then follow that across to the right until you hit the curve, hopefully you'll see that the x axis reads 120 degrees! Which is our answer anyway.

Answer 5

ok... thanks for the help :)