化简sin18度乘以cos36度
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化简sin18度乘以cos36度
结果是四分之一,
结果是四分之一,
![化简sin18度乘以cos36度](/uploads/image/z/15762530-2-0.jpg?t=%E5%8C%96%E7%AE%80sin18%E5%BA%A6%E4%B9%98%E4%BB%A5cos36%E5%BA%A6)
sin18°cos36°
=sin36°cos36°/(2cos18°)
=sin72°/(4cos18°)
=sin(90°-18°)/(4cos18°)
=cos18°/(4cos18°)
=1/4
=sin36°cos36°/(2cos18°)
=sin72°/(4cos18°)
=sin(90°-18°)/(4cos18°)
=cos18°/(4cos18°)
=1/4