求值sin80的平方[1+根3tan10]
求值；sin80的平方[1+根3tan10]/4[cos40-cos40的3次方
(sin80°)^2*(1+√3tan10°)/4[cos40°-(cos40°)3]
=(sin80°)^2*(1+√3*tan10°)/4[cos40°*(1-cos40°^2)]
=(sin80°)^2*(1+√3tan10°)/4[cos40°*(sin40°)^2]
=(sin80°)^2*(1+√3tan10°)/[2*(2cos40°*sin40°)*sin40°]
=(sin80°)^2*(1+√3tan10°)/(2*sin80°*sin40°)
=sin80°*(1+√3tan10°)/(...全部
求值；sin80的平方[1+根3tan10]/4[cos40-cos40的3次方
(sin80°)^2*(1+√3tan10°)/4[cos40°-(cos40°)3]
=(sin80°)^2*(1+√3*tan10°)/4[cos40°*(1-cos40°^2)]
=(sin80°)^2*(1+√3tan10°)/4[cos40°*(sin40°)^2]
=(sin80°)^2*(1+√3tan10°)/[2*(2cos40°*sin40°)*sin40°]
=(sin80°)^2*(1+√3tan10°)/(2*sin80°*sin40°)
=sin80°*(1+√3tan10°)/(2sin40°)
=cos10°*[1+√3(sin10°/cos10°)]/(2sin40°)
=(cos10°+√3sin10°)/2(sin40°)
=[(1/2)cos10°+(√3/2)sin10°]/sin40°
=(sin30°cos10°+cos30°sin10°)/sin40°
=sin(30°+10°)/sin40°
=1。
收起
