1. Triangles and Quadrilaterals

2. Triangles have the following characteristics:
They are polygons.
They have three sides.
They have three angles.
Their three angles total to 180°.
They can be classified by their sides.
They can be classified by their angles.
The sum of the length of any two sides is greater than the third side.
Triangles

3. Classifying Triangles by their Sides
Classify the following triangle by its sides:
equilateral
All 3 sides have the same length.
isosceles
At least two sides have the same length.
scalene
No sides have the same length.
5.5 cm
3 cm

4. Classifying Triangles by their Sides
Classify the following triangle by its sides:
equilateral
All 3 sides have the same length.
isosceles
At least two sides have the same length.
scalene
No sides have the same length.
5.5 cm
3 cm

5. Classifying Triangles by their Angles
acute
All three angles are acute angles (less than 90°).
obtuse
One angle is an obtuse angle (greater than 90°).
right
One angle is a right angle (equal to 90°).
Classify the following triangle by its angles:
92°
68°
20°

6. Classifying Triangles by their Angles
acute
All three angles are acute angles (less than 90°).
obtuse
One angle is an obtuse angle (greater than 90°).
right
One angle is a right angle (equal to 90°).
Classify the following triangle by its angles:
92°
68°
20°

7. Quadrilaterals have the following characteristics:
They are polygons.
They have four sides.
They have four angles.
Their four angles total to 360°.
They can be classified by the length and relationship of their sides.
They can be classified by the size and relationship of their angles.
Quadrilaterals

8. Classifying Quadrilaterals by their Sides and Angles
trapezoid
Exactly two sides are parallel.
parallelogram
Each opposite side is parallel and has the same length.
rectangle
Each opposite side is parallel and has the same length.
All angles are 90°.
rhombus
Each opposite side is parallel, and all sides have the same length.
square
Each opposite side is parallel, and all sides have the same length.

9. Missing Angles in Triangles and Quadrilaterals
What measure for angle B will make this quadrilateral a rectangle?
120°
60° B
80°
100°
75°
What must angle B measure so that this figure is a quadrilateral?
What measure for angle B will make this figure a triangle?
What must angle B measure so that this figure is a parallelogram?

10. Missing Angles in Triangles and Quadrilaterals
What measure for angle B will make this quadrilateral a rectangle?
90°
120°
60° B
80°
100°
75°
What must angle B measure so that this figure is a quadrilateral?
What measure for angle B will make this figure a triangle?
15°
What must angle B measure so that this figure is a parallelogram?

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