sin163°sin223°+sin253°sin313°的值为( )求详解,

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sin163°sin223°+sin253°sin313°的值为()求详解,sin163°sin223°+sin253°sin313°的值为()求详解,sin163°sin223°+sin253°si

sin163°sin223°+sin253°sin313°的值为( )求详解,
sin163°sin223°+sin253°sin313°的值为( )求详解,

sin163°sin223°+sin253°sin313°的值为( )求详解,
sin163°sin223°+sin253°sin313°
=sin(180º-17°)sin(180º+43°)+sin(270º-17°)sin(270º+43°)
=-sin17°sin43°+cos17°cos43°
=cos17°cos43°-sin17°sin43°
=cos(17°+43°)
=cos60°
=0.5