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September 1, 2014

September 1, 2014

Posted by **Omar** on Tuesday, October 11, 2011 at 9:19pm.

- trig -
**Reiny**, Tuesday, October 11, 2011 at 10:42pmuse

cos 2A = cos^2A - sin^2A

cos2A = cos^2A - (1 - cos^2A) = 2cos^2A - 1

cos 45° = 2cos^2 22.5° - 1

√2/2 + 1 = 2cos^2 22.5

√2/4 + 1/2 = cos^2 22.5°

cos 22.5° = √[ (√2 + 2)/4 ]

= √(√2 + 2) /2

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