â´ãf(x)=sin(x-Ï/4)-cos(x+Ï/4)=2sin(x-Ï/4)ï¼
ââãæå°æ£å¨æT=2Ïï¼
f(x)min=-2ï¼
âµãcos(β-α)=cosβcosα+sinβsinα=4/5ï¼cos(β+α)=cosβcosα-sinβsinα=-4/5ï¼
ââãcosβcosα=0ï¼sinβsinα=4/5ï¼
ââãcosβ=0ï¼ââãβ=Ï/2ï¼
æcosα=0ï¼ââãα=Ï/2ï¼ä¸åè¦æ±èå»ï¼
ââãf(β)=2sin(Ï/2-Ï/4)=â2ï¼
ââã[f(β)]^2-2=0ï¼
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