ANSWER
The point is
[tex](2, \sqrt{21} )[/tex]
EXPLANATION
The formula for finding the equation of a circle with centre,
[tex](a,b)[/tex]
and radius
[tex]r[/tex]
is given by
[tex] {(x - a)}^{2} + {(y - b)}^{2} = {r}^{2} [/tex]
The origin has coordinates
[tex](0,0)[/tex]
The equation of a circle centered at the origin with radius 5 units has equation
[tex] {x}^{2} + {y}^{2} = {5}^{2} [/tex]
or
[tex] {x}^{2} + {y}^{2} = 25[/tex]
When
[tex]x = 2[/tex]
Then we have,
[tex] {2}^{2} + {y}^{2} = 25[/tex]
This implies that,
[tex] 4 + {y}^{2} = 25[/tex]
[tex] {y}^{2} = 25 - 4[/tex]
[tex] {y}^{2} = 21[/tex]
[tex]y = \sqrt{21} [/tex]
