The distance between two points \( (x_1, y_1) \) and \( (x_2, y_2) \) is:
\[
d = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2}
\]
Substituting \( (x_1, y_1) = (2\cos \theta, 0) \) and \( (x_2, y_2) = (0, 2\sin \theta) \):
\[
d = \sqrt{(0 - 2\cos \theta)^2 + (2\sin \theta - 0)^2}
\]
\[
= \sqrt{4\cos^2 \theta + 4\sin^2 \theta}
\]
\[
= \sqrt{4(\cos^2 \theta + \sin^2 \theta)}
\]
\[
= \sqrt{4 \times 1} = \sqrt{4} = 2
\]