Periodic Functions

The graph begins to repeat itself at  ≈ 6.2832 which is 2π and that equals 360 ^o  
You can select any place on the graph and add 2π to the x value and the graph at that new point will begin to repeat.
Therefore the period for the cosine functions is 360^o or 2π the same as the sine function even
though the graph of the cosine function differs from that of the sine function.



Also adding 360^o(or 2π or a whole number multiple of either) to any angle and the value of the original cosine function will not change.

For instance the cos 7.236^o = cos (7.236 + 360)^o = cos (7.236 +720)^o all = .992035756 (To increase your understanding check this result with a calculator)
The answer means that the height on the vertical axis is always the same and hence the graph begins to repeat.

Remember that the horizontal axis is measured in radians (It could be measured in degrees but it would be cumbersome)

• Therefore what does 7.236^o equal in radians?
answer
• Once you have convert to radians will the cosine of that value
  differ from the value of cos 7.236^o?
answer
• In other words will the height above the horizontal axis be different
  for an angle if it is measured in radians instead of degrees or vice versa?
answer

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