1.
are adjacent angles.
2. The sum of the interior angles of a nonagon is 
3. The measure of angle4 is 
4. The sum of the interior angles of a regular polygon is 
5.the measure of the missing angle of a pentagon is 
Further Explanation:
The formula for the sum of angles of a polygon can be expressed as follows,

Explanation:
Part (1)
Adjacent angles are those angles that have common line and common vertex.
has the common vertex B and common line BC.
Therefore,
are adjacent angles.
Part (2)
Nonagon has 9 sides.
The sum of all the interior angles can be obtained as follows,

Part (3)
The measure of angle4 can be obtained as follows,

Part (4)
The polygonhas 12 sides.
The sum of all the interior angles can be obtained as follows,

Part (5)
The missing angle can be obtained as follows,

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Answer details:
Grade: Middle School
Subject: Mathematics
Chapter: Angles
Keywords: vertical angle, opposite angle, angles, alternate angles, linear pair, corresponding angles, adjacent angle, missing angle, n, 12 sides.