Sin3x*cos5x-sin5x*cos3x=-1

Question

Sin3x*cos5x-sin5x*cos3x=-1

Answer 1

  sin(3x-5x)=-1    sin(-2x)=-1        -sin2x=-1   sin 2x==1
  2x=π/2+2πn.  n∈Z
  x=π/4+πn.  n∈Z