cos(-45 )sin 405 - cos900 / tg (-p/3)ctg (-7p/3)

cos(-45°)sin(405°)-cos900°/tg(-60°)ctg(-420°)==cos45°.sin(360°+45°)-cos(720°+180°/tg60°ctg(360°+60°)==√2/2.sin45°-cos180°/√3ctg60°=(√2/2)(√2/2)-(-1)/√3.√3/3==2/4+1/(3/3)=1/2+1/1=1/2+1=3/2