1. Triangles and Quadrilaterals
Special names and properties for these polygons

2. Naming Triangles:
Triangles are named by observing their angles as well as their sides.
We have special names that correspond to their angles, and there are names that correspond to their sides.

3. Naming Triangles
If a triangle has just one angle which measures 90°, then the triangle is called a RIGHT triangle.
NOT Right Triangles
Right Triangles

4. Is it possible to have a triangle which has two 90° angles?
NOW what ??
Conclusion: There exists no triangles with two 90° angles.

5. Acute Triangle
If all 3 angles of a triangle measure less than 90°, then the triangle is an acute triangle.
NOT acute triangles
Acute Triangles

6. Obtuse Triangle
If just one angle of a triangle is greater than 90°, then the triangle is obtuse.
NOT obtuse triangles
Obtuse Triangles

7. Naming Triangles based on their side lengths:
A triangle is SCALENE, if none of the three sides are congruent.
NOT scalene triangles
Scalene Triangles

8. Equilateral Triangles
If all 3 sides of a triangle are congruent, then the triangle is equilateral.

9. Isosceles Triangles
If two sides of a triangle are congruent, then it is an isosceles triangle.
Isosceles Triangles
NOT isosceles triangles

10. Name these triangles as specific as possible:

11. QUADRILATERALS Every quadrilateral will fit into one of 6 categories.
Trapezoid, Kite, Parallelogram, Rhombus, Rectangle, and Square.
They depend upon how many sets of lines are parallel (0, 1, or 2), how many pairs of sides are congruent, and how many angles are congruent.

12. QUADRILATERAL FLOWCHART
QUADRILATERALS
How many sets of parallel sides does the quadrilateral have??
If there are 2 sets of parallel lines, then the figure is some type of PARALLELOGRAM!
If 0 is the answer, then the quadrilateral is a ‘KITE’.
If 0 is the answer, then the quadrilateral is a ‘KITE’.
If 1 is the answer, then the quadrilateral is a ‘TRAPEZOID’
‘RHOMBUS’
RECTANGLE
Both sets of lines are parallel, and all sides are congruent!
(IF the two non-parallel sides are congruent, it is an isosceles trapezoid)
SQUARE
All 4 sides equal, all 4 90° angles

13. TRAPEZOID
If a quadrilateral has just one pair of parallel lines, then it is a trapezoid

14. PARALLELOGRAM
A quadrilateral is a parallelogram if it has TWO sets of parallel lines

15. RHOMBUS
A quadrilateral is a RHOMBUS, if it has two sets of parallel lines AND all 4 sides are congruent.

16. RECTANGLE
A Quadrilateral is a Rectangle if it has two sets of parallel lines, and all 4 angles are congruent (RIGHT angles).

17. SQUARE
A quadrilateral is a square if it has two sets of parallel lines, 4 congruent sides, and 4 congruent angles (RIGHT angles).

18. KITE
This quadrilateral has no sets of parallel lines.

19. CLASSWORK/HOMEWORK
Page 64, #2-16
Page 65, 66, #25-29