求sin6°*cos24°*sin78°*cos48°的值
1个回答

sin6°*cos24°*sin78°*cos48°

=sin6°*cos24°*cos12°*cos48°

=16cos6°sin6°*cos24°*cos12°*cos48°/(16cos6°)

=8sin12°*cos12°*cos24°*cos48°/(16cos6°)

=4sin24°*cos24°*cos48°/(16cos6°)

=2sin48°*cos48°/(16cos6°)

=sin96°/(16cos6°)

=cos6°/(16cos6°)

=1/16