sin105°-cos105°
=√2(sin105°cos45°-cos105°sin45°)
=√2sin(105°-45°)
=√2sin60°
=√2*√3/2
=√6/2
（cosπ/12+sinπ/12）（cosπ/12-sinπ/12）
=cos²π/12-sin²π/12
=cosπ/6
=√3/2
1-2sin²π/8
=cos(π/4)
=√2/2