【用戶】張弄醒
【年級】國二下
【評論內容】由正弦定理 a/sinA = b/sinB = c/sinC 又角B=180°-30°-45°=105° a/sin30°=8/sin105 又sin105°=sin﹙60°+45°﹚ =sin60°cos45°+cos60°sin45° =﹙√3/2﹚﹙√2/2﹚+﹙1/2﹚﹙√2/2﹚ =﹙√6/4﹚+﹙√2/4﹚ 且 sin30°=1/2