Answer:
C) [tex]51^o[/tex]
Explanation:
As we know that angle in same quadrant with same magnitude is known as coterminal angle
so lets discuss each angle
a) [tex]591^o[/tex]
so we can say it is
[tex]540^o + 51^o[/tex]
so it is 51 degree with negative x axis in third quadrant
b) [tex]231^o[/tex]
so we can say it is
[tex]180^o + 51^o[/tex]
so it is 51 degree with negative x axis in third quadrant
c) [tex]51^o[/tex]
so it is 51 degree with negative x axis in third quadrant
d) [tex]-129^o[/tex]
so we can say it is
[tex]-180^o + 51^o[/tex]
so it is 51 degree with negative x axis in third quadrant
So coterminal angles are 591, 231 , -129
