BÀI 4 CMR   +    =X X X X5 3 7X XCOS .COS SIN SIN COS .COS 2...

1)

sin

4

sin

4

3

sin

4

5

sin

4

7

3

A

=

π

+

π

+

π

+

π

=

 

 

2

2

2

2

16

16

16

16

2