问一道数学题 sin(－1320)乘以cos1110＋cos(－1020)乘以sin720,最后再加上tan495,等于?

sin(-1320)=sin60
cos1110=cos30
cos(－1020)=cos60
sin720=sin0=0
tan495=-tan45
所以sin(－1320)*cos1110＋cos(－1020)*sin720+tan495
=sin60*cos30+cos60*0+(-tan45)
=3/4+0-1
=-1/4

呵呵 都有三个答案了

=sin(-360*4+120)*cos(360*3+30)+cos(-360*3+60)*sin(360*2)
=sin(120)*cos(30)+0
=sin(180-60)*sin(60)
=sin(60)*sin(60)
=3/4

sin(－1320°)cos1110°＋cos(－1020°)sin720°+tan495°
=sin(－1320°+1440°)cos(1110°-1080°)＋cos(－1020°+1080°)sin(720°-720°)+tan(495°-360°)
=sin120°cos30°＋cos60°sin0°+tan135°
=sin60°cos30°＋cos60°sin0°+tan(180°-45°)
=二分之根号3乘以二分之根号3+cos60°乘以0-tan45°
=四分之3+0-1
=-1/4

sin(-1320)cos1110+cos(-1020)sin720+tg495=sin(-1320+360x4)cos(1110-360x3)+cos(-1020+360x3)sin(720-360x2)+tg(495-360)=sin120cos30+0+tg135=sin60cos30-1=3/4-1=-1/4