Răspuns:
cos7π/12=cos(π/3+π/4)=
cosπ/3*π/4-sinπ/3*sinπ/4=
1/2*√2/2-√3/2*√2/2=
√2/2(1/2-√3/2)=
√2/2*2(1-√3)=
√2/4*(1-√3)
Explicație pas cu pas:
