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What's the meaning of cos x >_ U[ 2npi - pi/2 , 2npi + pi/2] And what does U denote?

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1 Answer

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U denotes union. This is read: cosx is greater than or equal to zero implies x is an element of the union [2npi-pi/2,2npi+pi/2] for all integers n.

So, for example, if you substitute n=1, you have cos x is greater than or equal to zero for [2pi-pi/2, 2pi+pi/2] which is true. The sentence is stating that this interval will hold when you substitute for any integer n.

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