Explicație pas cu pas:
Stiind ca x∈(0,π/2) si cosx=12/13 , calculati:
a) cos(x+π/6)
b) sin(x+π/3)
c) cos(x-π/6)
sinx=√(1-cos²x)=√(1-144/169)=√25/169=5/13
a) cos(x+π/6)=cosx*cosπ/6-sinx*sinπ/6=12/13*√3/2-5/13*1/2=
=12√3/26-5/26=(12√3-5)/26
b)sin(x+π/3)=sinx*cosπ/3+cosx*sinπ/3=5/13*1/2+12/13*√3/2=
=5/26+12√3/26=(12√3+5)/26
c)cos(x-π/6)=cosx*cosπ/6+sinx*sinπ/6=12/13*√3/2+5/13*1/2=
=12√3/26+5/26=(12√3+5)/26
Sa nu se mai intample asa ceva(ma refer la intrebarea pe care ai pus-o) , Altadata cand vei mai pune asa va fi stearsa si nu vei fi bucuroasa.
Bafta!
