问题
解答题
已知|
|
答案
由正弦定理
=|
|AC sinB
，得|
|BC sinA
=5.6 sinB
，sinB=4.2 sin40°
=0.8755.6×sin40° 4.2
∴B=59°，因为
-AC
与BC
夹角为B角的补角，即121°CB
∵C=180°-40°-59°=81°
∴|
|=AB AC2+BC2-2AC•BC•cosC
=
=6.4535.62+4.22-2×5.6×4.2cos81°
∵|
-BC
|=|AC
|∴|AB
-BC
|=6.453AC