sin2x-cos2x-1=√2 sin(2x-π/4) 这又是怎么化的?

sin2x-cos2x-1=√2 sin(2x-π/4) 这又是怎么化的?
sin2x-cos2x-1=√2 sin(2x-π/4) 这又是怎么化的?

sin2x-cos2x-1=√2 sin(2x-π/4) 这又是怎么化的?
sin2x-cos2x-1
=√2(sin2x×√2/2-cos2x×√2/2)-1
=√2sin(2x-π/4)-1
如果本题有什么不明白可以追问,

sin2x-cos2x
=√2( sin2x cos(π/4) -cos2xsin(π/4) )
=√2sin(2x-π/4)

sin(2x-π/4)
＝sin2xcosπ/4-cos2xsinπ/4
=sin2x-cos2x-1