The number of capital English alphabet vowels (A, E, I, O, U) that retain their original appearance when reflected in a mirror is determined by assessing each vowel's symmetry:
- A: Exhibits vertical symmetry; its mirror image is identical to the original.
- E: Lacks vertical symmetry; its mirror image differs from the original.
- I: Exhibits vertical symmetry; its mirror image is identical to the original.
- O: Possesses both vertical and horizontal symmetry, resulting in an identical mirror image.
- U: Exhibits vertical symmetry; its mirror image is identical to the original.
The vowels 'A', 'I', 'O', and 'U' maintain their original forms when mirrored. Consequently, 4 vowels retain their original appearance in a mirror.