Here's why:
* Stress: The word "widening" has stress on the first syllable ("wid").
* Unstressed Vowels: Unstressed vowels often have a reduced sound, often sounding like the vowel in the word "the" or "a".
* Pronunciation: The "i" in "widening" is pronounced with a reduced sound, almost like "uh".
So, the unstressed vowel in "widening" is the "i" in the second syllable, which has a reduced sound.