Prove, by induction, that the sum from 1 to n of cos2rX is
I can prove it by induction, although I am not certain if my logic is correct. Could anyone try this for me? Thanks.
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- Thread Starter
- 23-06-2004 13:32
- 23-06-2004 15:12
Is that : (sin(2r+1)X)/2(sinx +1)
or ((sin(2r+1)X)/2sinx) +1/2
or (sin(2r+1)X)/2sin(x +1)
- 23-06-2004 18:47
- 23-06-2004 19:21
If you want an alternative to induction you could use complex numbers or multiply the sum by sinx and use method of differences, although since the result is given, induction works easiest here
- 23-06-2004 21:58
The attached question (STEP 1990 Maths) is a nice example of using complex numbers to find trignometric sums.