Answers:
- cos(2theta) = -119/169
- cos(theta) = -5/13
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The given info is:
- sin(theta) = 12/13
- theta is in quadrant II
From that, we can use the pythagorean trig identity to find that cos(theta) = -5/13. Keep in mind that cosine is negative in quadrant II.
Now use the trig identity below to compute cos(2theta)
Other options you could use are these identities
or