计算:sin(π/12)sin(5π/12)要用二倍角与半角的公式

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计算:sin(π/12)sin(5π/12)要用二倍角与半角的公式计算:sin(π/12)sin(5π/12)要用二倍角与半角的公式计算:sin(π/12)sin(5π/12)要用二倍角与半角的公式s

计算:sin(π/12)sin(5π/12)要用二倍角与半角的公式
计算:sin(π/12)sin(5π/12)
要用二倍角与半角的公式

计算:sin(π/12)sin(5π/12)要用二倍角与半角的公式
sin(π/12)sin(5π/12)
=-1/2[cos(π/12+5π/12)-cos(π/12-5π/12)]
=-1/2(cosπ/2-cosπ/3)
=-1/2(0-1/2)
=1/4

1/4

sin(π/12)*sin(5π/12)
=sin(π/12)*cos(π/12)
=sin(2π/12)/2
=0.25