Arrange the given words in the sequence in which they occur in the dictionary.
i. Irrelevant
ii. Invincible
iii. Irresistible
iv. Invariable
v. Investigate

Let's determine the alphabetical order of the given words:
All words start with either "Inv..." or "Irr...". Since 'n' comes before 'r', "Inv..." words come first.

Comparing "Inv" words:

iv. Invariable ("Inva...") comes first.

ii. Invincible ("Invi...") and v. Investigate ("Inve..."). Comparing the 4th letter: 'e' comes before 'i', so Investigate comes before Invincible.

Therefore, the first three words are: iv, v, ii.

Comparing "Irr" words:

i. Irrelevant ("Irre...") vs iii. Irresistible ("Irre..."). Comparing the 5th letter: 'l' comes before 's', so Irrelevant comes first.

Therefore, the last two words are: i, iii.

Combining the sequence together, we get: iv, v, ii, i, iii.