How can I simplify [1-(k(sin^2) θ)] using trigonometric identities?

[princy]

hi..
i came through a problem in which the expression [1-(k(sin^2) θ)] has to be simplified.. can someone help me to solve it.??

 

[Simon Bridge]

Look for other forms of $\sin^2\theta$
http://www.sosmath.com/trig/Trig5/trig5/trig5.html