Here is a dynamic worksheet for teaching and reviewing some geometric relations such as sum of angles in a triangle, angles of parallelograms, corresponding angles, alternate-interior angles and more.

Teaching Suggestions:

Let the students explore the worksheet first by dragging the point on the sliders.

To show the measure of the angle (and if you wish, the area of the triangle), right click the angle and select ‘show value’. You can also change the size of the triangle by dragging A, B, or C.

Possible tasks:

1. Identify pairs of:

a. parallel lines

b. opposite angles of a parallelogram

c. alternate interior angles

d. corresponding angles, etc

2. Use the resulting figure in the applet to explain/ justify why the sum of angles in a triangle is 180 degrees.

3. Use the figure to explain why the measure of an exterior angle of a triangle is equal to the sum of the two remote interior angles.

I love to develop mathematical tasks and activities that involve basic mathematics concepts but have the potential to engage both teachers and students in higher level thinking. I am particularly interested in students’ learning trajectories of big ideas in number, algebra, geometry, and in the use of GeoGebra in learning mathematics. More. Email: linesronda@gmail.com

I love to develop mathematical tasks and activities that involve basic mathematics concepts but have the potential to engage both teachers and students in higher level thinking. I am particularly interested in students’ learning trajectories of big ideas in number, algebra, geometry, and in the use of GeoGebra in learning mathematics. More. Email: linesronda@gmail.com

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