2cos x - 1 ≥0

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Hi!I received your letter! I was glad of hearing from you as well! Thanks for your invitation. But I am compelled to upset you, I can't go with you on concert. The matter is that my parents are going to go  to the cinema and I will be compelled to nurse my little brother. On the next week i wiil be free and we can go on another concert. Thanks for understanding! Well will have fine.