84
tgx=3
x=arctg3+πn,n∈z
x={arctg3;arctg3+π;arctg3+2π}∈[0;3π]
87
ctg3x=1
3x=π/4+πn
x=π/12+πn/3,n∈z
-π/2<π/12+πn/3<π<br>-6<1+4n<12<br>-7<4n<11<br>-7/4n=-1⇒x=π/12-π/3=-π/4
n=0⇒x=π/12
n=1⇒x=π/12+π/3=5π/12
n=2⇒x=π/12+2π/3=9π/12=3π/4
90
y(3π/4)=tg(3π/4)=tg(π-π/4)=-tgπ/4=-1
y(3π/2)=tg(3π/2)=∞
E(y)∈(-1;∞)