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TRIANGLES AND QUADRILATERALS

Objectives

Name and classify triangles.

Name and classify quadrilaterals.

Find the measures of angles in these figures.

Vocabulary

Quadrilateral, parallelogram, rhombus, trapezoid, rectangle, square, equilateral triangle, isosceles triangle, scalene triangle, right triangle, acute triangle, obtuse triangle

 

Triangle is a popular shape to use in construction.  Triangles are rigid.  There are two ways to classify triangles by their side and by their angles.
Triangles have three sides, three vertices, and three angles.  The parts of the triangles are the height, or altitude, of a triangle is a line segment that starts at any vertex and is perpendicular to the opposite side of the triangle called the base.  To name a triangle, use the vertices.  Write  ABC Say:  Triangle ABC

Equilateral triangle all the sides have the same length.

 

 

Isosceles triangle two sides have the same length.

Scalene triangle no two sides have the same length.

Right triangle one right angle.

Acute triangle all angles are acute.

Obtuse triangle one obtuse angle.

 

 

The sum of the measures of the angles of any triangle is 180.

50 + 110 + 20 = 180

 

---------------------Try It Out---------------------------

Name each triangle according to the lengths of its sides.

 

1.

 

 

2.

 

3.

Name each triangle according to the measure of its angles.

 

4.

 

 

5.

 

Find the measure of the third angle in the triangle.

6.

 

 

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Quadrilaterals

Quadrilaterals is a closed 2-dimensional figure with four sides that are line segments.  some quadrilaterals have special traits, so they have special names.

Parallelogram has two pairs of parallel sides and two pairs of congruent sides.  In other words opposite sides the same length and parallel.

 

Rectangle is a parallelogram with four right angles.

 

 

 

 

Square is a parallelogram, rectangle, rhombus.  A square has four right angles and four congruent sides.

 

 

Rhombus is a parallelogram with four congruent sides.

 

 

Trapezoid has exactly one pair of parallel sides.

The sum of the measures of the angles of any quadrilateral is 360.

87 + 76 + 98 + 99 = 360

 

 

Classify each quadrilateral as many ways as you can.

1.

 

2.

 

 

3.

 

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Tangram Activity

Click here to take the quiz on triangles and quadrilaterals.

Remember to ask Ms.Painter for the password.

Triangles

Isosceles triangle Equilateral triangle Scalene triangle
Acute triangle Obtuse triangle 66 + 24 + x = 180

89 + x = 180

-89        -89

x = 91

 

 

 

 

 

 

 

 

 

 

 

 

Quadrilaterals

1) Parallelogram

Quadrilaterals

2) Quadrilateral

Parallelogram

Rectangle

3) Quadrilateral

Parallelogram

Rhombus

Rectangle

Square