Question

l1 and l2 are parallel lines. which angles are vertical angles? ∠dec and ∠deh ∠dec and ∠ghj ∠fec and ∠deh ∠ihj and ∠feh

Explanation:

Step1: Recall vertical - angle definition

Vertical angles are formed when two lines intersect, and they are opposite each other.

Step2: Analyze each option

• $\angle DEC$ and $\angle DEH$ are adjacent angles, not vertical angles.
• $\angle DEC$ and $\angle GHJ$ are not related as vertical angles.
• $\angle FEC$ and $\angle DEH$ are vertical angles because they are formed by the intersection of the lines $CF$ and $JI$ and are opposite each other.
• $\angle IHJ$ and $\angle FEH$ are not vertical angles.

Answer:

$\angle FEC$ and $\angle DEH$