Question 1019407
cosine (a - 360) should be equal to cosine (a).


this is because the graph of cosine (a) will repeat every 360 degrees.


here's what the graph looks like.


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the graph is of the equation y = cos(x).


there are 2 vertical lines.


one is at x = 30 and one is at x = 30 - 360.


30 - 360 is equal to - 330 as sh own on the graph.


you can see that the cosine function is the same for both angles.


using the trigonometric identity function of cos(a-b) should get you the same result when you assume that b is equal to 360 degrees.


the identity function is:


sin(a - b) = sin(a)cos(b) – cos(a)sin(b)


when b = 360 degrees, then


sin(360) = 0
cos(360) = 1


the formula of sin(a - b) = sin(a)cos(b) – cos(a)sin(b) becomes:


sin(a - 360) = sin(a)cos(360) - cos(a)sin(360) which becomes:


sin(a - 360) = sin(a)*1 - cos(a)*0 which becomes:


sin(a - 360) = sin(a)