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Sa se rezolve ecuatiile: a)cos(-x)=1/2 b)sin(x+pi/6)=-1/2

Răspuns :

cosx=1/2
 x=2kπ+-arccos1/2=2kπ+-π/3

x+π/6= k *π+(-1)^k *arcsin (-1/2)= kπ+(-1)^k * (-π/6)
x= kπ+(-1)^k * (-π/6)-π/6
=  kπ+ ( -1)^(k+1)π/6-π/6
 =kπ+[(-1) ^(k+1)-1]π/6  k∈Z
=2pπ+(-1-1)π/6∪ (2p+1)π+ (1-1)π/6=
 2pπ-π/3 ∪(2p+1)π, p∈Z
care verifica ecuatia