cmccindy
春芽
共回答了15个问题采纳率:93.3% 举报
∵sin(-53π/7)=sin(-8π+3π/7)
=sin(π/2-π/14)
=cos(π/14)
sin(-59π/8)=sin(-8π+5π/8)
=sin(π/2+π/8)
=cos(π/8)
又∵cosx在x∈[0,π]上是减函数,
而π/14cosπ/8
∴sin(-53π/7)>sin(-59π/8)
∵cos500°=cos(360°+90°+50°)
=cos(90°+50°)
=-sin50°
cos530°=cos(2×360°-170°)
=cos170°
=cos(90°+80°)
=-sin80°
又∵sin80°>sin50°
∴-sin80°cos530°
1年前
4