sin5/3π=sin(2π-1/3π)=-sin1/3π=-√3/2
(1/3π=60°)
cos8/3π=cos(2π+2/3π)=cos2/3π=-1/2
(2/3π=120°)
tan3/4π=tan(π-1/4π)=-tan1/4π=-1
(1/4π=45°)
sin5/3π+tan3/4π*cos8/3π=-√3/2+(-1)(-1/2)=-(√3-1)/2=-0.366