sin10sin30sin50sin70=多少

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sin10sin30sin50sin70=多少
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sin10sin30sin50sin70=多少
sin10sin30sin50sin70=多少

sin10sin30sin50sin70=多少
由sin(90-α)=cosα 和 2sinαcosα=sin2α 得：
sin10sin30sin50sin70
=cos80cos60cos40cos20
=cos80*1/2*cos40(cos20sin20)/sin20
=1/2*cos80cos40*1/2*sin40/sin20
=1/4*cos80*(cos40sin40)/sin20
=1/4*cos80*1/2*sin80/sin20
=1/8*cos80sin80/sin20
=1/8*1/2*sin160/sin20
=1/16sin(180-20)/sin20
=1/16sin20/sin20
=1/16

求值：sin10sin30sin50sin70 化简sin10sin30sin50sin70 sin10sin30sin50sin70= sin10sin30sin50sin70 求值 sin10sin30sin50sin70=多少 sin10sin30sin50sin70的值 求sin10sin30sin50sin70的值 求sin10sin30sin50sin70的值 sin10sin30sin50sin70的值= (是度）答案是1/16 我要过程 求sin10sin30sin50sin70的值(最好有过程),还有的就是sin20sin60sin100sin140=cos10cos30cos50cos70吗? (1/2)求值,1.sin10sin30sin50sin70 2.(2cos10-sin20)/cos20 3.(1+cos20)/2sin20 sin10sin30sin50sin70 =1/2sin1sin10sin30sin50sin70=1/2sin10sin50sin70=1/2sin10cos20cos40=1/2cos10cos10cos20cos40/cos10=1/4sin20cos20cos40/cos10=1/8sin40cos40/cos10=1/16sin80/cos10=1/16cos10/cos10=1/16第一步到第二步sim50sin70怎么变成了cos20