chopinn
种子
共回答了16个问题采纳率:87.5% 举报
(1)cos(π/5)+cos(2π/5)+cos(3π/5)+cos(4π/5)
=cos(π/5)+cos(2π/5)-cos(2π/5)-cos(π/5)
=0
(2)tan10°+tan170°+sin1866°-sin(-606°)
=tan10°+tan(180°-10°)+sin(5*360°+66°)-sin(-360°-246°)
=tan10°-tan10°+sin66°+sin246°
=sin66°+sin(180°+66°)
=sin66°-sin66°
=0
1年前
7