3)f(x)=tg5xf(π/15)=tgπ/3=√35)tg(4x-π/6)=√3/34x-π/6)=π/6+πn4x=π/3+πnx=π/12+πn/4,n∈Z7)2cos²5x-3sin5xcos5x+sin²5x=0 /cos²5x≠0tg²5x-3tg5x+2=0tg5x=aa²-3a+2=0a1+a2=3 U a1*a2=2a1=1⇒tg5x=1⇒5x=π/4+πn⇒x=π/20+πn/5,n∈Za2=2⇒tg5x=2⇒5x=arctg2+πn⇒x=1/5arctg2+πn/5,n∈Z