Witam proszę nawet o 1 zadanie mam 10 min dzięki!

The question in Englih
Hello, I am asking you for 1 task, I have 10 minutes thanks!

we have that  

a) cos(x)=-(√10)/10  for x ∈ [pi/2,pi]> [90°,180°]  I cuadrant
we know that
x=arccos (-(√10)/10)=108.43°
if 180°> pi radian
108.43°> X
X=108.43/180=0.60pi
the answer part a) is x=0.60pi (108.43°)

b) tan(x)=2    for x ∈ [pi,(3/2)pi]> [180°,270°] > III quadrant
we know that
x=arctan (2)=63.43°> ∉ III quadrant
therefore
x=180°+63.43°=243.43°
if 180°> pi radian
243.43°> X
X=243.43/180=1.35pi

the answer part b) is x=1.35pi (243.43°)

part c) 
x=2alfa
cos(x)=-1/3   for x∈ [(3/2)pi,2pi]> [270°,360°]> IV quadrant
we know that
x=arccos (-1/3)=109.47°> ∉ IV quadrant
therefore
x=109.47°+180°=289.47°
if 180°> pi radian
289.47°> X
X=289.47°/180°=1.61pi
 x=2alfa
alfa=x/2> 289.47°/2=144.74°
alfa=1.61pi/2=0.81pi

the answer part c) is alfa=0.81 pi (144.74°)

the answer in Polish

mamy to 

a) cos(x)=-(√10)/10  for x ∈ [pi/2,pi]> [90°,180°]  I cuadrant
wiemy to
x=arccos (-(√10)/10)=108.43°
if 180°> pi radian
108.43°> X
X=108.43/180=0.60pi
część odpowiedzi a) jest x=0.60pi (108.43°)

b) tan(x)=2    for x ∈ [pi,(3/2)pi]> [180°,270°] > III quadrant
wiemy to
x=arctan (2)=63.43°> ∉ III quadrant
w związku z tym
x=180°+63.43°=243.43°
if 180°> pi radian
243.43°> X
X=243.43/180=1.35pi

część odpowiedzi b) jest x=1.35pi (243.43°)

c) cos(x)=-1/3
x=2alfa
cos(x)=-1/3   for x∈ [(3/2)pi,2pi]> [270°,360°]> IV quadrant
wiemy to
x=arccos (-1/3)=109.47°> ∉ IV quadrant
w związku z tym
x=109.47°+180°=289.47°
if 180°> pi radian
289.47°> X
X=289.47°/180°=1.61pi
 x=2alfa
alfa=x/2> 289.47°/2=144.74°
alfa=1.61pi/2=0.81pi

część odpowiedzi c) jest alfa=0.81 pi (144.74°)