化简sin18*cos36

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化简sin18*cos36
化简sin18*cos36

化简sin18*cos36
sin18*cos36=sin18*cos36*sin72/sin72
=sin18*cos36*sin72/sin72
=sin18*cos36*cos18/sin72
=(sin18*cos18)*cos36/sin72
=(1/2sin36)*cos36/sin72
=1/4sin72/sin72
=1/4

乘以4cos18,再除以4cos18
4cos18*sin18*cos36/(4cos18)=2sin36*cos36/(4cos18)=sin72/(4cos18)=cos18/(4cos18)=1/4

sin18*cos36=sin18*cos18*cos36/cos18
=sin36*cos36/2cos18=sing72/4cos18=cos18/4cos18=1/4

sin18*cos36
=2sin18*cos18*cos36/(2cos18 )
=sin36*cos36/(2cos18)
=sing72/(4cos18)
=cos18/(4cos18)
=1/4

化简sin18*cos36 化简sin18*cos36答案是1/4, sin18°cos36° sin18*cos36=? 化简sin18度乘以cos36度结果是四分之一, 化简：cos36°(（sin18°)^2 -(sin72°)^2)-(sin36°)^2 三角函数化简sin18-cos36=-0. sin18°cos36°怎么解求cos36°sin18°的值 (sin18)平方+（cos36）平方,求值?怎么算? 求证：sin18度cos36度=1/4 求sin36,cos36,sin18,cos18的值用分数表示. 4（sin18°）平方+4（cos36°）平方三角函数推导(sin18°cos36°)^2=1/4(1+cos36°)(1-cos72°) 请教2cos18°×cos18°(sin18°-1)+cos36°sin18°的值, 已知sin18°=(√5-1)/4,则(cos36°)^2+(sin18°)^2= 计算cos36度*sin18度答案上写的是1/4，但是我不会算利用三倍角公式,求SIN18度,COS36度的值