7cos (2x-π/3) = -3.5|:7
cos (2x-π/3) = -1/2
2x-π/3=+-(π-arccos1/2)+2πn, n∈Z
2x-π/3=+-2π/3+2πn, n∈Z
2x=+-2π/3+π/3+2πn, n∈Z |:2
x=+-π/3+π/6+πn, n∈Z
x1=π/2+πn, n∈Z x2=-π/6+πn, n∈Z
3sin13/12П * cos 13/12П= 3*2/2<span>sin13/12П * cos 13/12П=
=3/2*2</span><span>sin13/12П * cos 13/12П = 3/2*Sin26/12</span>π = 1,5Sin(2π + π/6) =
= 1,5Sinπ/6 = 1,5 *1/2 = 0,75