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Trig questions, please help?
How do I find the exact value of these functions:
1. cos-1(cos 4π/5)
2. sin-1(sin 9π/8)
3. tan-1(tan 4π/5)
I'm geting the right values, just not the right sign. How do you know if they're negative or positive? Thanks!
1 Answer
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- DWReadLv 78 years agoFavorite Answer
Refer to the Even-Odd identities
cos(-4π/5) = cos(4π/5)
arccos(cos(-4π/5)) = arccos(cos(4π/5), so -4π/5 and 4π/5 are both solutions.
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