5cos²(x/2)-5sin²(x/2)+4sin(x/2)cos(x/2)-3sin²(x/2)-3cos²(x/2)=0
8sin²(x/2)-4sin(x/2)cos(x/2)-2cos²(x/2)=0 /cos²(x/2)≠0
8tg²(x/2)-4tg(x/2)-2=0
tg(x/2)=a
4a²-2a-1=0
D=4+16=20
a1=(2-2√5)/2=1-√5⇒tg(x/2)=1-√5⇒x/2=arctg(1-√5)+πn⇒x=2arctg(1-√5)+2πn
a2=(2+2√5)/2=1+√5⇒tg(x/2)=1+√5⇒x/2=arctg(1+√5)+πn⇒2arctg(1+√5)+2πn