SECTION 07
Worked Examples
Every problem type from the lesson, solved line by line in English. Open a card to reveal the full solution, then test the quick drills below.
Step-by-step solutions
- ∴A polygon must be plane, closed, and made only of line segments meeting at endpoints.
- ∴Any curve, opening, or crossing segment disqualifies the figure.
- ∴A closed figure with 5 segments is a pentagon; with 8 segments it is an octagon.
Visual classification drill
Quick drills — complete the following
Number of diagonals in a quadrilateral …
2
Number of diagonals in a pentagon …
5
Sum of interior angles of a heptagon …
900°
Sum of interior angles of a nonagon …
1,260°
One interior angle of a regular decagon …
144°
Axes of symmetry of a parallelogram …
0
Axes of symmetry of a regular hexagon …
6
Axes of symmetry of an isosceles trapezium …
1
A polygon with 8 sides is called …
an octagon
A polygon with one reflex interior angle is …
concave