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# Easy addition formulae question Watch

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1. tan of 15 degrees
2. (Original post by APersonYo)
tan of 15 degrees
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3. What the person above said... I think 😁😁

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4. (Original post by B_9710)
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What then?
5. (Original post by APersonYo)
What then?
You know the value of tan30, let t be tan15 and solve a quadratic in t.
6. (Original post by APersonYo)
tan of 15 degrees
Personally I would go with saying tan(15) = tan(60-45) and then expand using the addition formula for tan.

And if you're not familiar with the double angle formulae yet then this may be a better approach. If you haven't seen the double angle formulae then B_9710's method just uses tan(30) = tan(15 + 15).

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Updated: October 5, 2016
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