1. POLYGONS Polygons are 2-dimensional shapes
POLYGONS Polygons are 2-dimensional shapes. They are made of straight lines, and the shape is "closed" (all the lines connect up).
Polygon (straight sides)
Not a Polygon (has a curve)
Not a Polygon (open, not closed)
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2. POLYGONS Regular Polygons all sides are equal and all angles are equal otherwise they are Irregular Polygons.
Regular Polygons
Irregular Polygons
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4. Types of Angles Acute angle: an angle that is less than 90°
Right angle: an angle that is exactly 90° (shown by drawing a little box)
Obtuse angle: an angle that is greater than 90° but less than 180°
Straight angle: an angle that is exactly 180°
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5. Quadrilateral A figure with 4 straight sides.
The angles inside of the figure ALWAYS add up to be 360°
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6. Parallelogram
A Parallelogram is a flat shape with opposite sides parallel and equal in length.
The angles that are diagonal from one another are equal. (in the example above angles "a" are the same, and angles "b" are the same)
Angles "a" and "b" add up to 180° and if you add all four angles up you get 360°

7. Triangles A triangle has three sides and three angles.
The three angles always add to 180°
There are three different kinds of triangles:
Equilateral Triangle
Three equal sides Three equal angles, always 60°
Isosceles Triangle
Two equal sides Two equal angles
Scalene Triangle
No equal sides No equal angles

8. What does congruent mean?
Two shapes need to be the same size to be congruent.
Angles can also be congruent. They have to have the same degree.
These angles are congruent.