why cos 70 = -cos 110?

👨🏻‍🏫 學術台數學

megan

2011-03-20 12:23 am

why does cos 70 = -cos 110?

回答 (1)

[匿名]

2011-03-20 12:28 am

You need to look at the full definition of the cosine function to know why.
http://www.youtube.com/watch?v=ZffZvSH285c

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