Question 967615
Simplify the expression by using a double-angle formula. 
cos^2 (3pi/11) - sin^2 (3pi/11) 

Please let me know if this is correct: I think this is an identity problem. 
cos (2A) = cos^2 A - sin^2 A 
would the expression simplify to: 
cos(2 (3pi/11)) =6pi/11
you got it correct