[size=100]In this lesson, you will use Geogebra to explore some basic geometric postulates. [br][br][b][i]When you get to a question that has the word "POSTULATE" in it, after checking your answer WRITE DOWN the correct formulation of that Postulate in your notes![/i][/b][/size]

Look at the figure below and consider this question: Is it possible to identify a line using only one point? [br][br]If I talked about "line E" in the figure below, what line would I be talking about?[br][br]Click on one of the blue points and drag it to see if that changes your mind.

Look at the figure below and consider these questions: [br][br]How many [b]different lines[/b] could I draw that go through points A and B? [br][br]How many different lines could I draw that go through points A, B and C? (Remember, "lines" in geometry means STRAIGHT paths with no curves).[br][br]Try clicking on the line tool [icon]https://www.geogebra.org/images/ggb/toolbar/mode_join.png[/icon] within the line menu [icon]/images/ggb/toolbar/mode_join.png[/icon]and then click on various points. You can undo your work with the UNDO icon in the upper right. Try to draw a line through all three points.[br][br]Now click back on the MOVE tool [icon]/images/ggb/toolbar/mode_move.png[/icon] and drag point C around. Can you drag it to a location where a single line could be drawn that contains points A, B and C?

For this postulate we will consider two lines.[br][br]Drag the various blue points around and consider this question:[br][br]What are the possible number of points of intersection for two lines?

For this postulate, we will consider the position of two points on a line.[br][br]Use the POINT tool to add two points to plane. Click the point A button, then click anywhere in the grey parallelogram. Use the MOVE tool [icon]https://www.geogebra.org/images/ggb/toolbar/mode_move.png[/icon] to click and drag the plane and check the position of the points. , [br]Then use the LINE tool [icon]https://www.geogebra.org/images/ggb/toolbar/mode_join.png[/icon] to draw a line through the two points you created.[br][br]Where is the line's position on the plane? Can you draw the line so that it is on the plane? Can you draw the line so that it is intersecting the plane, but not on it? Can you draw the line off the plane?