(1)
sina*cosa*(tana+1/tana)
=sinacosa*tana+sinacosa/tana
=sinacosa*sina/cosa+sinacosa*cosa/sina
=sin²a+cos²a
=1
(2)
sin(-a)*cos(2π+a)*tan(-a-π)
=-sina*cosa*(-tana)
=sinacosa*cosa/sina
=sin²a
如果你认可我的回答,请点击左下角的“采纳为满意答案”,祝学习进步!