1)sin 90градусов*sinx=2sin45 градусов*sin x/2

sin90=1; sin45=
sinx=sinx/2 => 2sinx/2cosx/2-sinx/2=0 => 
sinx/2(2cosx/2-)=0 => 
sinx/2=0 => x/2=пk => x=2пk;
Cosx/=/2 => x/2=п/4+2пk => x=п/2+4пk и x/2= -п/4+2пk => x= - п/2+4пk