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# sine/cosine/tangent squared question watch

1. Hi 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

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

Thankyou!!
2. Square root and remember there are two square roots.
3. You simply square root.

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

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