tan2π=0 cot(-5π/2)=0

sin(-11π/3)+cos(12π/5)tan2π-sec13π/5cot(-5π/2)
=sin(-11π/3)
=sin(-4π+π/3)
=sinπ/3
=√3/2为什么最上面的两个式子等于0sin2π=0 cos2π=1 tan2π=sin2π/cos2π=0cos(-5π/2)=0 sin(-5π/2)=1 cot(-5π/2)=cos(-5π/2)/sin(-5π/2)=0