Answer:
GTLN : 1 GTNN: -1
Step-by-step explanation:
Ta có:
[tex]y=cos(x+\frac{\pi }{3} ) + cos(x-\frac{\pi }{3} ) \\ = 2.cosx.cos\frac{\pi }{3} \\ = cosx[/tex]
mà [tex]-1\leq cosx \leq 1[/tex]
Nên Max [tex]y=1[/tex] , [tex]x[/tex] ∈ [tex]R[/tex]
Min [tex]y = -1[/tex], [tex]x[/tex] ∈ [tex]R[/tex]
