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March 2, 2015

March 2, 2015

Posted by **Michael** on Sunday, March 21, 2010 at 9:14pm.

- Trigonometric -
**Reiny**, Sunday, March 21, 2010 at 11:02pmsometimes it is easier to think in degrees, and then switch back

7π/12 = 105 degrees and 105 = 60+45

both angles that we know

cos 105

= cos(60+45)

= cos60cos45 - sin60sin45

= (1/2)(√2/2) - (√3/2)(√2/2)

= (√2 - √6)/4

so cos7π/12 = (√2-√6)/4

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