



 
Hi Saban, You haven't given us the instruction s for this problem but you are probably looking to write this expression in terms of sin a and cos a. To accomplish this you need to use the identities
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Penny and Stephen La Rocque. Saban, There are many choices for identities here. For example, you can write the cosine of an even multiple of 'a' as a polynomial in (cos a)^2. To make it easier to read, I will let x = (cos a)^2. By using basic trig identities and a lot of patience you can easily see that cos 2a = 2x  1 Chris  


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