1) 5π/6+π/4 =13π/12; π/3 + π/2 =5π/6; 1 +π/6 = 1 +π/6;
coosπ/6 = 1/2;
2) = (1/3 *x - π/3) =πn, n∈Z; 1/3*x =πn +π/3; x = 3πn +π; n∈Z;
=2x =2π/3 +2πn,n∈Z; x = π/3 +πn,n∈Z;
2cosx -1 =0; 2cosx = 1; cosx =1/2; x =+- π/3+2πn,n∈Z;
sinx = √2/2; x = [tex] (-1)^{n} \pi /4 + \pi n, n∈Z;