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sin15度×Cos15度=

SIN15º=SIN(60º-45º)=SIN60ºCOS45º-SIN45ºCOS60º=(√6-√2)/4 COS15º=COS(60º-45º)=COS60ºCOS45º+SIN60ºSIN45º=(√6+√2)/4 sin15°+cos15°= 2 ( 2 2 sin15°+ 2 2 cos15°)=...

sin15°=sin(45° - 30°) =sin45°cos30° - cos45°sin30° =√2/2 * √3/2 - √2/2 * 1/2 =(√6 - √2)/4 cos15°=cos(45° - 30°) =cos45°cos30°+sin45°sin30° =√2/2 * √3/2+√2/2 * 1/2 =(√6+√2)/4 tan15°=sin15°/cos15° =[(√6-√2)/4] / [(√6+√2)/4] =(√6-...

sin15°=sin(60°-45°)=sin60°cos45°-cos60°sin45° =√6/4-√2/4=(√6-√2)/4 cos15°=√(1-sin15°的平方)=(√6+√2)/4

sin15°=(45°-30°)=sin45°cos30°-cos45°sin30°=(6^0.5-2^0.5)/4=(根号6-根号2)/4 你也可以用其他三角函数公式求解!

等于。

由倍角公式sin2a=2sinacosa 所以sin15cos15 =1/2*(2sin15cos15) =1/2*sin2*15 =1/2*sin30 =1/2*1/2 =1/4

解: sin15° =sin(45°-30°) =sin45°cos30°-cos45°sin30° =√2/2×√3/2-√2/2×1/2 =(√6-√2)/4 cos15° =cos(45°-30°) =cos45°cos30°+sin45°sin30° =√2/2×√3/2+√2/2×1/2 =(√6+√2)/4 tan15° =tan(45°-30°) =(tan45°-tan30°)/(1+tan45°tan3...

sin15 * cos15 = 1/2 * sin30 = 0.25 望采纳+谢谢。

sin2a=2sinacosa sinacosa=sin2a/2=sin30/2=(1/2)/2=1/4

cos15°-sin15° =1-sin15°÷cos15° (同时除以cos15°) =1-tan15°

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