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daca x apartine (0, \pi /2) si cos x= \sqrt{2} /2,aratati ca tg x=1.



Răspuns :

x=2kπ+-arccos√2/2=2kπ+-π/4
cum x∈(0;π/2)⇒x=π/4
tgx=tgπ/4=1 , C.C.T.D.
as simple as that!


x apartine (0, \pi /2) si cos x= \sqrt{2} /2

x∈(0,  π/2),  cosx = √2/2 ⇒ x = π/4

tgx = tg(π/4) = 1