






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 180º. 50º + 110º + 20º = 180º

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.

Quadrilaterals 
Quadrilaterals is a closed 2dimensional 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 360º. 87º + 76º + 98º + 99º = 360º

Classify each quadrilateral as many ways as you can. 

2.

3.


Click here to take the quiz on triangles and quadrilaterals. Remember to ask Ms.Painter for the password. 
Isosceles triangle  Equilateral triangle  Scalene triangle 
Acute triangle  Obtuse triangle  66 + 24 + x =
180
89 + x = 180 89 89 x = 91º 

1) Parallelogram
Quadrilaterals 
2) Quadrilateral
Parallelogram Rectangle 
3) Quadrilateral
Parallelogram Rhombus Rectangle Square 