The distance from the origin is a.
Step-by-step explanation:
If the point is located at the coordinate [tex](a\cos \alpha, a\sin \alpha)[/tex], then its distance from the origin is given by
[tex]r = \sqrt{x^2 + y^2} = \sqrt{(a\cos \alpha)^2 + (a\sin \alpha)^2}[/tex]
[tex]\:\:\:\:=\sqrt{a^2(\cos^2\alpha + \sin^2 \alpha)}[/tex]
[tex]\:\:\:\:= a[/tex]
