sin315度- cos135度+2sin570度=
问题描述：
sin315度- cos135度+2sin570度=
答
1/10*12
=1/2*2/10*12
=1/2*(12-10)/10*12
=1/2*(12/10*12-10/10*12)
=1/2*(1/10-1/12)
所以1/10*12+1/12*14+1/14*16+1/16*18
=1/2*(1/10-1/12+1/12-1/14+1/14-1/16+1/16-1/18)
=1/2*(1/10-1/18)
=1/45
答
=(-sin45)-(-cos45)+2(-sin30)
=-√2/2+√2/2-1
=-1