sin(-1470度)cos1740度+cos(-660度)sin750度tan405
=sin(-1440-30)cos(1800-60)+cos(-720+60)sin(720+30)tan(360+45)
=sin(-30)cos60+cos60sin30tan45
=-1/2*1/2+1/2*1/2*1
=0
sin(-1470度)cos1740度+cos(-660度)sin750度tan405
=sin(-1440-30)cos(1800-60)+cos(-720+60)sin(720+30)tan(360+45)
=sin(-30)cos60+cos60sin30tan45
=-1/2*1/2+1/2*1/2*1
=0