1-2sinx cosx /COS^2X-SIN^2X =1-tanx/1+tanx 求证
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![1-2sinx cosx /COS^2X-SIN^2X =1-tanx/1+tanx 求证](/uploads/image/z/2095586-26-6.jpg?t=1-2sinx+cosx+%2FCOS%5E2X-SIN%5E2X+%3D1-tanx%2F1%2Btanx+%E6%B1%82%E8%AF%81)
1-2sinx cosx /COS^2X-SIN^2X =1-tanx/1+tanx 求证
1-2sinx cosx /COS^2X-SIN^2X =1-tanx/1+tanx 求证
1-2sinx cosx /COS^2X-SIN^2X =1-tanx/1+tanx 求证
这里用到:(sin)^2+(cosx)^2=1,
原式=(cosx-sinx)^2/(cosx+sinx)(cosx-sinx)
=(cosx-sinx)/(cosx+sinx)
=(1-tanx)/(1+tanx).