3TGX TGΠ −X TG Ữ  Π +XỮ=TG XTG A G A3 3SIN SIN

2)

.

.

3

tgx tg







π

−

x tg

 

ữ 

 

π

+

x



ữ



=

tg x

tg a

g a

3

3

sin

sin .cos

a

−

a

b

+

cos a

=

+



+





−



=

−

AD: tính

.

⁷

.

¹³