Question

116, пожалуйста
13.116 решите пожалуйста

Answer 1

8sin²15π/16*cos²17π/16-1
sin²15π/16=sin²(15π/16-π)=sin²(π/16)
cos²17π/16=cos²(17π/16-π)=cos²(π/16)
8sin²(π/16)cos²(π/16)-1=2sin²π/8-1=-cosπ/4=-√2/2

sin⁴23π/12-cos⁴13π/12=sin⁴(23π/12-2π)-cos⁴(13π/12-π)=
=sin⁴(11π/12)-cos⁴(11π/12)=(sin²11π/12+cos²11π/12)(sin²11π/12-cos²11π/12)=
=-cos22π/12=-cos11π/6=-cos(11π/6-2π)=-cosπ/6=-√3/2