BA
2
2 24
1
2
3 2 a b = = = = 90
6
( ) ()
3
( ) ()
3
( ) ()
3
7
1 4 ab
= = = =
2 4 ab =
=
3 4 ab + = 180
3
a 5
7 8
6
1
3 4
2
b
c
4
a 5
7 8
6
1
3 4
2
b
c
