Interior Angles

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On the graph below, the arrows pointed to the right mean that the two lines are parallel. [br]Measure ONLY the interior angles: ([math]\angle DFG,\angle GFC,\angle AHG,\angle GHB[/math]).[br]Then color the congruent angles the same color.

Which line above is the "transversal line"?

Here, the congruent angles are a rotation of each other.[br][br]For example, if you rotate Angle DFG 180 degrees around Point G, it will end up at Angle AHG.[br][br]These are called "Alternate Interior Angles" [br][br]"Alternate" means they are on opposite sides of the transversal line (one on the left and one on the right).[br][br]"Interior" means they are in between the parallel lines (inside the parallel lines).

Which angle is Alternate Interior with [math]\angle DFG[/math]?

Which angle is Alternate Interior with [math]\angle BHG[/math]?

Which definition best describes Alternate Interior Angles?

They are in matching corners of two parallel lines. They are on opposite sides of the transversal and inside the parallel lines. They form a straight line. The are across from each other over intersecting lines. (opposite sides of an X).

Which transformation best describes Alternate Interior Angles?

Translations Reflections Rotations

Looking at your graph above, finish this conjecture: "If a transversal crosses two parallel lines, then Alternate Interior Angles are always..."

Complimentary Congruent Supplementary

Look at your graph again. Angle DFG and Angle BHG are called "Same Side Interior Angles".[br][br]"Same side" means they are on the same side of the transversal line (both on the right).[br][br]"Interior" means they are in between the parallel lines (inside the parallel lines).

If Angle DFG and Angle BHG are Same Side Interior Angles, what other pair of angles could be considered Same Side Interior?

Add up the measure of the Same Side Interior Angles. What do you notice?

Which definition best describes Same Side Interior Angles?

They are in matching corners of two parallel lines. They are on the same side of the transversal and inside the parallel lines. They are on opposite sides of the transversal and inside the parallel lines. They form a straight line.

Finish this conjecture: "If a transversal crosses two parallel lines, then Same Side Interior Angles are always..."

Supplementary Complimentary Congruent

Assume Line BD and Line EG are parallel.

Which pair of angles listed below are Alternate Interior?

[math]\angle4[/math] & [math]\angle8[/math] [math]\angle3[/math] & [math]\angle6[/math] [math]\angle2[/math] & [math]\angle7[/math] [math]\angle1[/math] & [math]\angle2[/math]

Which pair of angles listed below are Same Side Interior?

[math]\angle1[/math] & [math]\angle2[/math] [math]\angle2[/math] & [math]\angle7[/math] [math]\angle4[/math] & [math]\angle6[/math] [math]\angle3[/math] & [math]\angle6[/math]

What is the measure of the green angle pictured above?

What is the measure of the pink angle pictured above?

Which Geometry word describes angles that are the same size?

Which Geometry word describes angles that add up to 180 degrees?

Assume Lines BD and EG are parallel.

In the diagram above, if Angle 5 is 100 degrees, then what is the measure of Angle 4?

Interior Angles

Assume Line BD and Line EG are parallel.

Assume Lines BD and EG are parallel.

Information: Interior Angles