SOLUTION: if sinθ= √5/3, then cos2θ equals can you please show the steps!

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Question 441871: if sinθ= √5/3, then cos2θ equals
can you please show the steps!
Answer by Gogonati(809) About Me  (Show Source):
You can put this solution on YOUR website!
sin%28theta%29=sqrt%285%29%2F3 As you know, cos%282%2Atheta%29=1-2%28sin+%28theta%29%29%5E2
Substitute in the last identity: cos%282%2Atheta%29=1-2%28sqrt%285%29%2F3%29%5E2, and find
cos%282%2Atheta%29=-1%2F9.