化简:sin780°cos1110°+cos(-660°)sin(-690°)+tan585°cos1440°
问题描述：
化简:sin780°cos1110°+cos(-660°)sin(-690°)+tan585°cos1440°
答
sin(2x360+60)cos(3x360+30)+cos(-2x360+60)sin(-2x360+30)+tan(360+225)cos(4x360)
=sin60cos30+cos60sin30+tan(180+45)
=√3/2 x √3/2+1/2 x 1/2 - √2/2
=1-√2/2