4sinx + 2cosx=0 sin5x sinx - cos5x cosx=1\2 cos7x + cos3x=0

1)2tgx+1=0; 2tgx=-1; tgx=-1/2; x=-arctg0,5+πn 2)-(cos5x cosx-sin5x sinx)=1/2   -cos(5x+x)=1/2   cos6x=-1/2  6x=+-(π-π/3)+2πn 6x=+-(2π/3)+2πn x=+-π/9+π/3 *n 3)2cos((7x+3x)/2) *cos((7x-3x)/2)=0    2cos5x cos2x=0   cos5x=0       ili           cos2x=0   5x=π/2 +πn                  2x=π/2+2πn  x=π/10+π/5 *n                  x=π/4 +πn