[salim 97]

( sin2x= cos(x+p/6 تكافئ( cos(p/2-2x

يعني ان (p/2-2x = -x-p/6+2KP او p/2-2x = x+p/6+2K)

ومنه (x=p/9-2KP/3 او x= 2p/3 - 2KP)

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