(2cos20°-sin10°) / sin80° 단순화하여 평가하다.

(2cos20°-sin10°) / sin80° 단순화하여 평가하다.

(2cos20°-sin10°)/sin80°=(2cos20°-cos80°)/sin80°=[cos20°+(cos20°-cos80°)]/sin80°={cos20°+[cos(50°-30°)-cos(50°+30°)]}/[sin80°]={cos20°+[2sin30°sin50°]}/sin80°={cos20°+s
(2cos20°-sin10°) / sin80° = 루트호3