Bell WorkThe length of segment AB

is 5 ⅙ cm and the length of segment BC is 9 ⅕ cm.

What is the length of segment AC?

Bell Work Answer5 ⅙ + 9 ⅕ =

5 5/30 + 9 6/30= 14 11/30

LESSON 2

:

ANGLES, P

OLYGONS,

TRIA

NGLES A

ND

QUADRILATE

RALS

If two lines cross we say that they intersect. The place where the lines intersect is called the point of intersection.

Two lines in the same plane either intersect or do not intersect. If two lines in the same plane do not intersect, we say that the lines are parallel.

If two lines make square corners at the point of intersection we say that the lines are perpendicular. The angles made by the perpendicular lines are called right angles.

Two right angles form a straight angle.

Acute Angle*An angle smaller than a right angle.

Obtuse Angle*An angle greater than a right angle but less than a straight angle.

If a right angle is divided into 90 parts, we say that each part has a measure of 1 degree. Thus, a right angle has a measure of 90 degrees which can also be written as 90°.

Two right angle form a straight angle. Thus, a straight angle has a measure of what?

What would 4 right angles have a measure of?

Polygon*:A special kind of geometric figure with more than one angle.

Examples of non-polygons

Line segments cannot cross. Polygons have to be closed. Circles are not polygons.

Polygon Examples:

Triangle3 sides3 vertices

Quadrilateral4 sides4 vertices

Pentagon5 sides5 vertices

Polygon Examples

Hexagon6 sides6 vertices

Heptagon7 sides7 vertices

Octagon8 sides8 vertices

Polygon Examples

Nonagon

Decagon

Undecagon

Dodecagon

Concave*:When a polygon has an indentation or a cave.

Convex*:Any polygon that does not have an indentation.

If all the sides of a polygon have the same length, the polygon is called equilateral.

If all the angles of a polygon have the same measure, the polygon is called equiangular.

If all the sides have the same length and all the angles have the same measure then the polygon is called regular.

A regular triangle is called equilateral.

What would a regular quadrilateral be called?

Triangles:Contain 3 sides and 3 angles. The sum of the measures of the three angles will always add up to 180 degree.

If a triangle has a right angle, the triangle is a right triangle.

If all angles have a measure less than 90 degrees, the triangle is acute.

If one angle is greater than 90 degrees, the triangle is obtuse.

An equiangular triangle is when all the angles are equal. If a triangle’s angles always add up to 180°, then what is the measure of each angle?

How are each of these triangles classified?

PRACTICE:

Matching:Parallelogram, trapezoid, rectangle, rhombus, square

Practice:A, B and C on Page 8

HW: Lesson 2 #1-30