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January 27, 2015

January 27, 2015

Posted by **Anna** on Thursday, March 28, 2013 at 12:27pm.

- Trig -
**Steve**, Thursday, March 28, 2013 at 1:29pmSince sin = -12/13 in QIV, cos = 5/13

sec x/2 = 1/cos(x/2) = √(2/(1+cosx))

= √(1/(1+5/13)) = √(2/(18/13)) = √(26/18) = √13/3

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