sin(-1200°）×cos1290°+cos(-1020°)×sin（-1500°）+tan945°
=sin(1440-1200)×cos(1080+210)+cos(1080-60)×sin(-1440-60)+tan(720+225)
=sin240°×cos210°+cos60°×sin(-60°)+tan225°
=sin60°×cos30°-cos60sin60°+tan45°
=3/4-√3/4+1
=7/4-√3/4