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**Triangles and Quadrilaterals**

Special names and properties for these polygons

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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.

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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

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**Is it possible to have a triangle which has two 90° angles?**

NOW what ?? Conclusion: There exists no triangles with two 90° angles.

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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

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

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**Naming Triangles based on their side lengths:**

A triangle is SCALENE, if none of the three sides are congruent. NOT scalene triangles Scalene Triangles

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**Equilateral Triangles**

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

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

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**Name these triangles as specific as possible:**

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**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.

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**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

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

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

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

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

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

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KITE This quadrilateral has no sets of parallel lines.

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

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