Trigonometry

I just want to know if this answer is correct, 120/169.

Use identities to find the indicated value for each angle measure.

sin θ = 12/13, cos θ > 0
Find cos (2θ).

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  1. You know it will be in quadrant 2 where cos is negative

    cos^2-sin^2 = 25/169 - 144/169 = -119/169

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  2. Cos0= -3/5 where pie over 2 _<0 < pie
    Fin tan 20 could you explain how to get the answer?

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