Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ π -¹ ² ³ °

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**tony123****Member**- Registered: 2007-08-03
- Posts: 189

*Last edited by tony123 (2007-08-05 13:21:31)*

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**JaneFairfax****Member**- Registered: 2007-02-23
- Posts: 6,868

First you show that sin80° = sin40° + sin20°. I have set this as a separate exercise for you to do:

http://www.mathsisfun.com/forum/viewtop … 580#p76580

∴

*Last edited by JaneFairfax (2007-08-07 11:53:15)*

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**Ricky****Moderator**- Registered: 2005-12-04
- Posts: 3,791

Reason #131 why I hate trig.

"In the real world, this would be a problem. But in mathematics, we can just define a place where this problem doesn't exist. So we'll go ahead and do that now..."

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**MathsIsFun****Administrator**- Registered: 2005-01-21
- Posts: 7,560

Nice job there Jane.

"The physicists defer only to mathematicians, and the mathematicians defer only to God ..." - Leon M. Lederman

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**George,Y****Member**- Registered: 2006-03-12
- Posts: 1,306

You've been so patient Janefairfax.

**X'(y-Xβ)=0**

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**Identity****Member**- Registered: 2007-04-18
- Posts: 934

Wow. That is amazing!

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