In this question we are working with a periodic function (the "cos" function) it means it has a pattern and it repeats itself as the time passes, and once it repeats is self in cycles this cycles are called periods. to understand it let's take a look at the cos function:
We saw above the cos function has some values for all values of x but there are special numbers as x=0, x=1 and x=-1 where the cos function is mos represented because these are its maximums and mins. So, all the 360 degrees are an cycle that represent a period, we can represent the cos function is another way as follows:
So for our function we have:
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With coordinates it can be represented as follows: