用“>”或“

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用“>”或“
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用“>”或“
用“>”或“

用“>”或“
好几年没遇个三角函数了,不过这是我拿手好戏,凭记忆来做吧,有错请谅解哈,cos40°=sin50°,原式=sin50°^2-1/2,在0~90度内sinx单调递增,既sin50°^2>sin45°^2=[sqr(2)/2]^2=1/2,故填“>”
注:“^”表示平方,“sqr”表示平方根.

sin50°乘以cos40°-1/2=sin^2(50)-1/2
sin^2(60)=3/4
sin^2(30)=1/4
(3/4+1/4)/2=1/2 又sin(50)的值更偏向sin(60) 也就是更偏向3/4
于是sin(50)cos(40)>1/2
>

sin(50°) = 0.76604444311898
cos(40°) = 0.76604444311898
sin50°乘以cos40°等于0.586824089
sin50°乘以cos40°-1/2(>)0