asinx+bcosx=根号(a^2+b^2)*sin(x+另一个角),这个“另一个角”的正切=b/a,是公式,
sin2x-cos2x=根号(1+1)*(sin2x*根号2/2 -cos2x*根号2/2 )
根号2/2 =cos45=sin45=sinpai/4;
sin2x*根号2/2 -cos2x*根号2/2 =sin2x*cos pai/4-cos2x*sin pai/4=根号2*sin(2x-pai/4)
属于三角函数的知识
=1-cos2x+sin2x到下一步是怎么想的啊?=1+根号2*sin(2x-pai/4)
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