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Figure 1
A. SUMATIVE TEST for Written work
Answer the following:
1. Without drawing a nonagon, determine the number of its diagonals.
2. How many diagonals does a decagon have?
3. How many vertices does a triangle a triangle have?
4. How many vertices does a square have?
5. How many vertices does a pentagon have?
6-8. Do you observe any relationship between the number of sides of a polygon and the
number of its vertices? Explain your answer.
9. When is a triangle a regular polygon? Why?
10. When is a polygon a regular polygon?

1.To find the total number of diagonals in a polygon, multiply the number of diagonals per vertex (n - 3) by the number of vertices, n, and divide by 2 (otherwise each diagonal is counted twice).

2. Ten (10) sides

3. Three(3) Vertices

4. Four(4) Vertices

5. Five(5) vertices

6-8. ?

9.Regular and Irregular Polygon

Examples of regular polygon: In the adjoining figure of an equilateral triangle ABC there are three sides i.e., AB, BC and CA are equal and there are three angles i.e., ∠ABC, ∠BCA and ∠CAB are equal. Therefore, an equilateral triangle is a regular polygon.

10.A polygon is regular when all angles are equal and all sides are equal (otherwise it is "irregular"). This is a regular pentagon (a 5-sided polygon).

Step-by-step explanation:

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