Parallel Lines Properties of Angles Formed by Parallel Lines and a Transversal
Parallel lines (Definition) A line that intersects both parallel lines is called a transversal. Which is the transversal in the diagram above?
Parallel lines
Corresponding Angles
Alternate Angles (they alternate…) Alternate Interior: inside the parallel lines, on either side of the transversal Alternate Exterior: outside the parallel lines, on either side of the transversal
Same Side Interior These angles are on the same side of the transversal and inside the parallel lines.
Investigation 1) Use the ruler to draw a pair of parallel lines, intersected by a transversal. Label the angles. 2) Place a piece of patty paper over angles 1,2,3 and 4. Copy them onto the patty paper. 3) Slide the patty paper down to compare angles 1-4 with angles 5-8 4) Measure angle 1. Use this measure to calculate the measure of the other 7 angles.
Links to Geogebra Given one angle, Find others ggb Given one angle, Find others ggb All angles ggb All angles ggb
Theorems If two parallel lines are intersected by a transversal then: Corresponding Angles are equal Alternate Interior Angles are equal Alternate Exterior Angles are equal Same Side Interior Angles are supplementary
I Do: Find the measure of each angle. Justify.
We Do: Find the measure of each angle. Justify.
Your turn: Find the measure of each angle. Justify.
We Do: Find the value of x.
Your Turn: Find the value of x.
Geometry in nature…
Geometry around us…
Exit Slip What did we do today? What did you learn? What part of the lesson helped you learn it better? What are you still confused about?