cos23π/5 cos37π/4 谁大

显示全部楼层 · 2012-12-9 23:29:58

cos(23π/5)=cos(4π+3π/5)=cos(3π/5)=-cos(2π/5)cos(37π/4)=cos(9π+π/4)=-cos(π/4)因为π/2＞2π/5＞π/4＞0所以cos(2π/5)＜cos(π/4)-cos(2π/5)＞-cos(π/4) 故cos(23π/5)大...

千问 · 2012-12-9 23:29:58

cos(23π/5)=cos(4π+3π/5)=cos(3π/5)=-cos(2π/5)cos(37π/4)=cos(9π+π/4)=-cos（π/4）cos在0到π上是减函数2π/5=8π/20π/4=5π/208π/20>5π/20即2π/5>π/4所以cos(2π/5)-cos（π...

千问 · 2012-12-9 23:29:58

cos37π/4...