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sin10sin30sin50sin70=多少 急呀!!!!!

sin10*sin30*sin50*sin70 =cos10*sin10*sin30*sin50*sin70/cos10 =1/2*sin20*sin70*sin30*sin50/cos10 =1/2*sin20*cos20*sin30*sin50/cos10 =1/4sin40*sin50*sin30/cos10 =1/4sin40*cos40*sin30/cos10 =1/8sin80*sin30/cos10 =1/8cos10*sin30/co...

1.解sin10*sin30*sin50*sin70 =cos10*sin10*sin30*sin50*sin70/cos10 =1/2*sin20*sin70*sin30*sin50/cos10 =1/2*sin20*cos20*sin30*sin50/cos10 =1/4sin40*sin50*sin30/cos10 =1/4sin40*cos40*sin30/cos10 =1/8sin80*sin30/cos10 =1/8cos10*sin3...

证明: sin10°sin30°sin50°sin70° =1/2sin10°cos10°sin50°sin70°/cos10° =1/4sin20°sin50°cos20°/cos10° =1/8sin40°cos40°/cos10° =1/16sin80°/sin80° =1/16

sin10=cos80 cos20=sin70 sin30=cos60 cos40=sin50 sin90=1 sin10cos20sin30cos40sin50cos60sin70cos80sin90 =(sin10cos20sin30cos40)^2 =...

请问您问的是什么呢?

10=90-80

S=(1/2)sin10°sin50°sin70°=(1/2)[cos80°cos40°cos20°] cos20°cos40°cos80° ====>>> 分子分母同乘以8sin20°,分子连续使用sin2a=2sinacosa 答案:S=1/16

答案为;1/2, 4sin10sin50sin70 =4cos80cos40cos20 =4cos80cos40cos20sin20/sin20 =2cos80cos40sin40/sin20 =sin80cos80/sin20 =2sin80cos80/2sin20 =sin160/2sin20 =1/2 其实不止这一种方法,还有很多种,记得给我加分啊,谢谢啊1

分子 分母 同时乘以 cos10° sin10°×sin50°×sin70° = sin10°×sin50°×sin70°× cos10°/cos10° = sin10°× cos10°×sin50°×sin70°/cos10° = (1/2) × sin20°× sin50°× sin70°/cos10° = (1/2) × sin20°× sin50°× cos20°/cos10° = (1/4) × sin40°× sin50°...

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