sin6°cos24°sin78°cos48°=( - 知识问答

sin6°cos24°sin78°cos48°=( )

1个回答

原式=sin6°cos24°cos12°cos48°
=cos6°sin6°cos12°cos24°cos48°/cos6°
=sin12°cos12°cos24°cos48°/2cos6°
=sin24°cos24°cos48°/4cos6°
=sin48°cos48°/8cos6°
=sin96°/16cos6°
=cos6°/16cos6°
=1/16

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