cos43°cos77°+sin43°cos167°=?

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cos43°cos77°+sin43°cos167°=?cos43°cos77°+sin43°cos167°=?cos43°cos77°+sin43°cos167°=?cos43°cos77°+sin

cos43°cos77°+sin43°cos167°=?
cos43°cos77°+sin43°cos167°=?

cos43°cos77°+sin43°cos167°=?
cos43°cos77°+sin43°cos167°
=cos43°cos(90°-13°)+sin43°cos(180°-13°)
=cos43°sin13°-sin43°cos13°
=sin13°cos43°-cos13°sin43°
=sin(13°-43°)
=sin(-30°)
=-sin30°
=-1/2

cos43°cos77°+sin43°cos167°
=cos43°cos77°+sin43°sin(90°-167°)
=cos43°cos77°-sin43°sin77°
=cos(43°+77°)
=cos120°
=cos60°=1/2