1
4sin³x=cos(2π+π/2-x)
4sin³x-sinx=0
sinx(4sin²x-1)=0
sinx=0⇒x=πn,n∈z
4sin²x=1
4(1-cos2x)/2=1
2-2cos2x=1
2cos2x=1
cos2x=1⇒2x=2πk⇒x=πk,k∈z
2
-42tg34+tg(90-34)+6=-42tg34*ctg34+6=-42*1+6=-36
3
7√2*sin(2π-π/8)*cos(2π-π/8)=7√2*(-1/2*sinπ/4)=-7√2*1/2*√2/2=-3,5