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August 30, 2015
Posted by **Maddie** on Tuesday, November 27, 2012 at 11:26pm.

- trig -
**Steve**, Tuesday, November 27, 2012 at 11:29pmwell, you know that

siny = 3/5

cos2y = 1 - 2sin^2 y

or, you know that

tan 2y = 2tany/(1-tan^2 y)

and sec^2 2y = 1 + tan^2 2y

good way to check your answer.