sin347度cos148度＋sin77度cos58度＝？

sin347°cos148°+sin77°cos58°
=sin(360°-13°)cos(180°-32°)+sin(90°-13°)cos(90°-32°)
=(-sin13°)*(-cos32°)+cos13°sin32°
=sin13°cos32°+cos13°sin32°
=sin(13°+32°)
=sin45°
=√2/2

解：原式=sin(360-13)*cos(180-32)+sin(90-77)*cos58
=-sin13*(-cos32)+cos13*cos58
=sin13*sin58+cos13*cos58
=cos45
=0.707

莫名其妙