sin与cos关系求值：sin6°×sin42°× - 知识问答

sin与cos关系求值：sin6°×sin42°×sin66°×sin78°

1个回答

in6°sin42°sin66°sin78°
=sin6°cos12°cos24°cos48°
=16cos6°sin6°cos12°cos24°cos48°/16cos6°
=8sin12°cos12°cos24°cos48°/16cos6°
=4sin24°cos24°cos48°/16cos6°
=2sin48°cos48°/16cos6°
=sin96°/16cos6°
=cos6°/16cos6°
=1/16

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