BÀI 5 TÍCH( ( ) ) ( ( ) )
3) CMR
a b
b c
c a
+
−
0
2cos 10
2
1
tg
a tg
a
a
a
+
b
+
c
+
d
=
+
+
+
sin
sin
sin
sin
4sin
.sin
.sin
( ) ( ) ( )+
− =
0
0
35
25
2
2
2
( )+
+
a
3) CMR
a b
b c
c a
+
−
0
2cos 10
2
1
tg
a tg
a
a
a
+
b
+
c
+
d
=
+
+
+
sin
sin
sin
sin
4sin
.sin
.sin
( ) ( ) ( )+
− =
0
0
35
25
2
2
2
( )+
+
a