Evaluate the sum .

Note: The numbers are in degrees, example:

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- March 22nd 2008, 01:51 PMmath sucksHard Trigonometry
Evaluate the sum .

Note: The numbers are in degrees, example: - March 22nd 2008, 02:11 PMMoo
Hello,

Let N be this sum.

If you replace the sinus with cosine, you'll get something interesting :

So replace for each term.

You'll have :

But we know that

So if we replace again :

(1)

The aim will be to retrieve N in the brackets. So tihere is missing and an extra .

sin(0)=0, so we can remove . As sin(90°)=1,

By using (1) :

And then you have N ;)