利用诱导公式
sin(-23π/6)+cos13π/7*tan4π-cos13π/3
=sin(-23π/6+4π)+cos(13π/7)*tan(4π-4π)-cos(13π/3-4π)
=sin(π/6)+cos(13π/7)*tan0-cos(π/3)
=1/2+0-1/2
=0