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sine/cosine/tangent squared question

Hi :smile: I'm not sure if this is even an A level question but if

I know cosx = 0.5 then x = cos-1(0.5)
...but what if...
cos2x = 0.5 x = ??? I'm sure it's simple but I don't know how to deal with cosine squared :confused:

I've worked an equation through (from a question on radians) and ended up with tan2x=1/3.

Thankyou!!
Square root and remember there are two square roots.
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Avatar for 01Chris02
01Chris02
13
You simply square root.

EDIT: Oh Mr M beat me to it, and yeah two roots, a positive and negative solution :smile:
(edited 11 years ago)
Original post by Mr M
Square root and remember there are two square roots.


Cheers :smile:

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