Question

which angles are vertical to each other? ∠11 and ∠12 ∠11 and ∠9 ∠15 and ∠6 ∠3 and ∠16

Explanation:

Step1: Recall vertical - angle definition

Vertical angles are formed when two lines intersect. They are opposite each other and are congruent.

Step2: Analyze each option

• $\angle11$ and $\angle12$ are adjacent angles, not vertical angles.
• $\angle11$ and $\angle9$ are vertical angles as they are formed by the intersection of two lines and are opposite each other.
• $\angle15$ and $\angle6$ are not related as vertical - angles.
• $\angle3$ and $\angle16$ are not vertical angles.

Answer:

$\angle11$ and $\angle9$