cos^2 x - 2sinxcosx - sin^2 x = 0 [ 0 ≤2x≤ pi ]cos^2 x - 2sinxcosx - sin^2 x = 0 [ 0 ≤2x≤ pi ]

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cos^2 x - 2sinxcosx - sin^2 x = 0 [ 0 ≤2x≤ pi ]cos^2 x - 2sinxcosx - sin^2 x = 0 [ 0 ≤2x≤ pi ]
cos^2 x - 2sinxcosx - sin^2 x = 0 [ 0 ≤2x≤ pi ]
cos^2 x - 2sinxcosx - sin^2 x = 0 [ 0 ≤2x≤ pi ]

cos^2 x - 2sinxcosx - sin^2 x = 0 [ 0 ≤2x≤ pi ]cos^2 x - 2sinxcosx - sin^2 x = 0 [ 0 ≤2x≤ pi ]
原式=cos2x-sin2x=2^(1/2)*cos(2x+pi/4)=0,因为0