4sin3a*cos3a / 5cos3a = 4sin3a / 5
=4*(-0,5) / 5 = -0,4
(sin6a2sin3acos3a)
3cos²x+5sinxcosx+cos²x+sin²x=0
sin²x+5sinxcosx+4cos²x=0 /cos²x≠0
tg²x+5tgx+4=0
tgx=a
a²+5a+4=0
a1+a2=-5 U a1*a2=4
a1=-4⇒tgx=-4
x=-arctg4+πn
a2=-1⇒tgx=-1⇒x=-π/4+πn
Х(2а+в)+3у(в+2а)=(2а+в)(Х+3у)