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#1 2007-10-21 06:55:18

tony123
Member
Registered: 2007-08-03
Posts: 228

inequality

Prove that for every natural n the following inequality is valid:

|sin 1| + |sin 2| + |sin(3n-1)| + |sin(3n)| > 8n/5.

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#2 2007-10-21 07:03:23

mathsyperson
Moderator
Registered: 2005-06-22
Posts: 4,900

Re: inequality

Surely it's not?

You've got 4 sin functions on the left, and each individual term is never >1, which means that the left side is never >4.

Setting n=5 makes the right side become 8 and so the inequality is false.


Why did the vector cross the road?
It wanted to be normal.

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