Difference between revisions of "Angle sum property"
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*Non digital : Worksheet and pencil. | *Non digital : Worksheet and pencil. | ||
*Geogebra files : | *Geogebra files : | ||
| − | *#'''“[https://ggbm.at/wjdsrz4w | + | *#'''“[https://ggbm.at/wjdsrz4w a. Angles in a right triangle.ggb]” ,''' |
| − | *#'''“[https://ggbm.at/a2jjgpkn | + | *#'''“[https://ggbm.at/a2jjgpkn b. Angle sum property proof.ggb]” ,''' |
| − | *#'''“[https://ggbm.at/fskbjzxj | + | *#'''“[https://ggbm.at/fskbjzxj c. Angle sum property of a triangle.ggb]”''' |
===Process (How to do the activity)=== | ===Process (How to do the activity)=== | ||
| − | *Use the file - “[https://ggbm.at/wjdsrz4w | + | *Use the file - “[https://ggbm.at/wjdsrz4w a.Angles in a right triangle.ggb]” |
*Ask students what is the kind of triangle they observe. | *Ask students what is the kind of triangle they observe. | ||
*Draw a parallel line to the side containing the right angle through the opposite vertex by dragging point D along the x-axis | *Draw a parallel line to the side containing the right angle through the opposite vertex by dragging point D along the x-axis | ||
| Line 23: | Line 23: | ||
*Students should be able to recognize the alternate angles formed. Is the alternate angle same as one of the angles of the triangle. | *Students should be able to recognize the alternate angles formed. Is the alternate angle same as one of the angles of the triangle. | ||
*So what can you say about the all the angles of the triangle? | *So what can you say about the all the angles of the triangle? | ||
| − | *With the file - “[https://ggbm.at/a2jjgpkn | + | *With the file - “[https://ggbm.at/a2jjgpkn b. Angle sum property proof.ggb]” |
*Draw a line perpendicular to a side passing through the opposite vertex. How many triangles are formed. What kinds of triangles are formed? | *Draw a line perpendicular to a side passing through the opposite vertex. How many triangles are formed. What kinds of triangles are formed? | ||
*In each of the two triangles if on angle is 90<sup>o</sup>, what will be the sum of the other two angles. What is the sum of these angles? | *In each of the two triangles if on angle is 90<sup>o</sup>, what will be the sum of the other two angles. What is the sum of these angles? | ||
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!What can you say about sum of angles? | !What can you say about sum of angles? | ||
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| − | *With the file – “[https://ggbm.at/fskbjzxj | + | *With the file – “[https://ggbm.at/fskbjzxj c. Angle sum property of a triangle.ggb]” |
*Ask students what happens when the three angles of the triangle are placed adjacent to each other. | *Ask students what happens when the three angles of the triangle are placed adjacent to each other. | ||
*What can you say about the line drawn? | *What can you say about the line drawn? | ||
Revision as of 16:06, 12 April 2019
The angle sum property of a triangle states that the angles of a triangle always add up to 180°. Every triangle has three angles and whether it is an acute, obtuse, or right triangle, the angles sum to 180°
Objectives
- To establish the angle sum property of a triangle
- To help visualization of the geometric proof
Estimated Time
Prerequisites/Instructions, prior preparations, if any
Prior understanding of point, lines and angles, adjacent angles, vertically opposite angles, linear pair, parallel lines, alternate angles, corresponding angles.
Materials/ Resources needed
- Digital : Computer, geogebra application, projector.
- Non digital : Worksheet and pencil.
- Geogebra files :
Process (How to do the activity)
- Use the file - “a.Angles in a right triangle.ggb”
- Ask students what is the kind of triangle they observe.
- Draw a parallel line to the side containing the right angle through the opposite vertex by dragging point D along the x-axis
- Students should be able to recognize the corresponding angles formed when the parallel line is drawn.
- Students should be able to recognize the alternate angles formed. Is the alternate angle same as one of the angles of the triangle.
- So what can you say about the all the angles of the triangle?
- With the file - “b. Angle sum property proof.ggb”
- Draw a line perpendicular to a side passing through the opposite vertex. How many triangles are formed. What kinds of triangles are formed?
- In each of the two triangles if on angle is 90o, what will be the sum of the other two angles. What is the sum of these angles?
- Children can record the values of the angles of a triangle in the worksheet
| Observation | Angle 1 | Angle 2 | Angle 3 | Angle 1 + Angle 2 + Angle 3 | What can you say about sum of angles? |
|---|---|---|---|---|---|
| . | |||||
| . | |||||
| . |
- With the file – “c. Angle sum property of a triangle.ggb”
- Ask students what happens when the three angles of the triangle are placed adjacent to each other.
- What can you say about the line drawn?
- Is it parallel to one of the sides?
- What can you say about the pairs of angles – look at the matching colors.
- Once the parallel line reaches the vertex, how many angles are formed?
- Students should be able to identify the two angles moving are corresponding angles as the line moving is parallel to one of the sides.
- Students can see that when the three angles of the triangle are placed adjacent to each other they form a straight line.
Evaluation at the end of the activity
- Have students able to conclude if the sum of angles in any triangle is 180o?