ctg x = 2,05

sin²x = 1

cos²x = 1/2

1)ctgx=2,05⇒x=arcctg2,05+πn,n∈z2)sin²=1(1-cos2x)/2=11-cos2x=2cos2x=-12x=π+2πn,n∈zx=π/2+πn,n∈z3)cos²x=1/2(1+cos2x)/2=1/21+cos2x=1cos2x=02x=π/2+πn,n∈zx=π/4+πn/2,n∈z