sin2230’cos2230’=

sin2230’cos2230’=

利用二倍角公式：
sin2A=2sinAcosA
sin22.5*cos22.5
=1/2*sin45
=1/2*根号2/2
=根号2、4

sin2230’cos2230’
=2sin22.5度cos22.5度/2
=sin45度/2
=2^(1/2)/2/2
=2^（1/2）/4