TITLE: Geometry Lesson: Types of Triangles and Coordinate Grids

GRADE LEVEL: Middle School

CONTENT AREAS: Geometry

GUIDING QUESTION:

LEARNING TARGET/GOAL: 

 Students will understand how to find coordinate points in a coordinate grid.

EALR'S AND GLE'S: 

 Math 1.3: describe location of objects on coordinate grids.

DAY: ONE

OBJECTIVE(S): After a teacher led review of the types of triangles and an introduction to the concept of the x,y coordinate system, the students will be able to play a game involving the use of the coordinate system and show understanding of how coordinates are found.

EALR'S AND GLE'S:  Math 1.3

MATERIALS NEEDED:  Grid paper divided into two coordinate grids, one for each student.

PROCEDURES:

Agenda

Review Triangles

Introduce Coordinate system

Play Game

“First off today we’re going to quickly review the different types of triangles.  Does anyone remember one type?  And how is that kind of triangle classified?  What’s different about that type?”

On Board:

Triangles

                Equilateral            Isosceles               Scalene                  Right                      Acute                     Obtuse

                                                Two equal

                                                sides

Three equal sides                                No equal sides                      Has a 90° angle    All angles less                                                                                                                                                                                                     One

Than 90°               angle larger

                                Than 90°

“Any questions?”

“So now we’ll talk about the coordinate system.  Has anyone seen the coordinate system before?  Legend has it that this man, Descartes, was lying in bed looking at the ceiling, and he saw a fly up there.  He was bored, so he started thinking of a way he could describe the location of the fly on the ceiling using numbers, and he ended up inventing coordinate geometry.  Coordinate geometry is like using two number lines at the same time.”

On board draw x and y axis and put numbers on them.

“This number line, the side to side or horizontal one, is called the x axis.  And this number line, the up and down or vertical one, is called the y axis.  Any point in this area can be described by giving its number on the x axis and then its number on the y axis.  Give me a number for the x axis.  Okay, now for the y axis.  So that would be right here.  Where the x axis and the y axis meet, is zero on both number lines.  And just like on the other number lines we use, if we go below zero we start to find negative numbers.  Someone give me a negative number for the x axis.  Now let’s use a positive number for the y axis.  That would be right here.  If I want to find a point with the coordinates of (2,6), what do I do first?”

Answer: locate 2 on the x axis.

“Now what do I do?”

Answer: locate 6 on the y axis.

Put up three coordinates and have students practice in pairs discussing how to find those coordinates.  Have a volunteer come up and put the coordinate point on the board.

“Now we’re going to play a game that is kind of like Battleship.  It’s called find my triangle.  You will need a partner, and two pieces of this grid paper.  The paper already has the x and the y axis marked on it.  The rules are pretty simple.  Don’t let your partner see, and draw one of each type of triangle on your paper, so that the corners are on a grid point.  The triangles need to not have any sides that are longer than four grid squares.  And they can’t overlap. Then you take turns guessing where your partner’s triangles are.  You guess by giving them a grid coordinate, which has to be the x number, and then the y number.  If you got a corner, they tell you so, and if you got inside a triangle they tell you that.  When you’ve found all the corner of a triangle, they tell you which one you found.  Keep track by making marks on your paper.  Any questions?”

On board:

1.                  Draw one of each type of triangle on your paper, no more than four grid squares to a side and no overlapping!

2.                   Take turns guessing by calling out a grid coordinate (x,y)

3.                   If it’s a corner, say Corner!  If it’s inside the triangle say Area!  If they’ve found all the corners say what kind of triangle it is.

4.                   Keep track by making marks on your paper.                                    

POST-ASSESSMENT

Give students a set of coordinates and have them plot them on grid paper and draw the triangles they would form.  Collect and review these papers.

TEACHER REFLECTION (don't fill in this column until you teach the unit)