求值sin160*cos160*(tan340*+cot340*)的答案

sin160*cos160*(tan340+cot340)=sin(180-20)*cos(180-20)*[tan(360-20)+cot(360-20)=sin20*(-cos20)*(-tan20-cot20)=sin20*cos20*(tan20+cot20)=sin20*cos20*(sin20/cos20+cos20/sin20)=sin^2 20+cos^2 20=1