NO1:三角形面积为:(1/2)AC*AB*sinA
带入数值,得AC = 1
故:角B = 30° 角 C = 90°
所以BC = √3
NO2:三角形ABC三边之比为a:b:c=3:5:7,且其中最大边边长为14
所以a = 6,b = 10,c = 14
根据余弦定理:a^2=b^2 +c^2 -2bcCOSA
COSA = (b^2 + c^2 - a^2)/(2bc) = 13/14
sinA = √(1 - (COSA)^2) = 5/14
故三角形ABC的面积为:(1/2)bcsinA = 5√27