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在计算若干角度同名三角函数值连乘积的问题时,若能巧妙地应用公式:sinθsin(60°-θ)sin(60°+θ)=1/4sin 3θ;cosθcos(60°-θ)cos(60°+θ)=1/4cos 3θ;tgθtg(60°-θ)tg(60°+θ)tg 3θ。往往是相当奏效的,下面仅就一个例子说明这些公式的应用。
In the calculation of the product of the product of several angles with the same name of the trigonometric function, the formula can be applied wisely: sinθsin(60°-θ)sin(60°+θ)=1/4sin 3θ; cosθcos(60°-θ)cos( 60°+θ)=1/4cos 3θ; tgθtg(60°-θ)tg(60°+θ)tg 3θ. It’s often quite effective. Here’s just an example of how these formulas are used.