Hello,
Let's see the denominator :
Hence
Do you see the thing ? Do you see which formula for cos(2b) you will have to use ?
So
Now this is the tricky thing :
How did I know it ? Because I know where I want to go
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Seeing that I thanked you for your hard work, please help with this one
http://www.mathhelpforum.com/math-he...h-problem.html