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1. 2/5
2. 100, 91, 82, 73, 64
3. 96,48,24,12,6
4. -99
5. 1024/59049
6. a) 30, 39, 49, 60, 72 (I'm not sure though)
b) I can't get it!
7. I'm not sure about recursive formulas!
8. a) 3/256...

You may not need to further expand tan into sine and cosine!
that is ; If you know tan(a-b) = (tan a - tan b)/(1 + tan a tan b)

Evaluate the left hand side, then cross multiply to get a common...