Illustrative Mathematics
Joining Two Midpoints of Sides of a Triangle
Without ever using the actual term, this exercise has the learner develop the key properties of the midsegment of a triangle. This task leads the class to discover a proof of similar triangles using the properties of parallel...
Curated OER
Parallelism in Our Everyday World: Parallel Lines and Beyond
Students broaden their outlook on geometry in their everyday environment. They explore the properties of parallel lines and parallelograms and discover ways to prove the existence of parallel lines and discuss the concept of parallel lines.
Mathematics Assessment Project
Classifying Equations of Parallel and Perpendicular Lines
Parallel parking might be difficult, but finding parallel lines is fairly simple. In this lesson, learners first complete an assessment task involving parallel and perpendicular lines in the coordinate plane. Individuals then take part...
EngageNY
Informal Proofs of Properties of Dilations
Challenge the class to prove that the dilation properties always hold. The instructional activity develops an informal proof of the properties of dilations through a discussion. Two of the proofs are verified with each class member...
EngageNY
Angles Associated with Parallel Lines
Explore angle relationships created by parallel lines and transversals. The 13th lesson of 18 prompts scholars use transparency paper to discover angle relationships related to transversals. Learners find out that these angles pairs are...
EngageNY
Unknown Angle Proofs—Proofs of Known Facts
Lead the class in a Greek history instructional activity with a geometric twist. Pupils relate a short video about geometric properties to modern-day methods of solving for unknown angles. They discuss parallel line...
Virginia Department of Education
Properties of Quadrilaterals
What type of quadrilateral is that? Discover the difference between the types of quadrilaterals. Small groups investigate types of quadrilaterals using geometry software to find their properties. To keep track of the different...
Curated OER
Constructing Parallel Lines
Students construct parallel lines using a protractor and a straightedge. In this geometry lesson plan, students identify the properties of parallel lines. They use Cabri to graph and observe the lines.
Curated OER
Investigating the Slopes of Parallel and Perpendicular Lines
High schoolers investigate parallel and perpendicular lines. They use Cabri Jr. to construct and explore the relationships between the slopes of parallel and perpendicular lines. The drawing and measurement tools available with Cabri Jr....
Curated OER
Properties of Special Quadrilaterals
Teach your mathematicians how to identify the properties of quadrilaterals. In this geometry lesson, students solve for missing angles and sides of a special quadrilateral. They use the TI to move the sides around and create different...
Curated OER
Are We Sure They Are Parallel?
Fourth graders explore the definition and properties of parallel lines. This high level lesson has students calculate the slope of the two parallel lines, and draw the lines on a Caretsian coordinate system.
Curated OER
Lines, Lines, Everywhere
Students explore linear equation suing real life scenarios. In this algebra lesson plan, students find the slope and intercept of a line. They create table of values to plot their graph and draw conclusions.
Curated OER
Parallel and Perpendicular Lines
Tenth graders explore parallel and perpendicular lines. In this geometry lesson, 10th graders investigate the relationships associated with parallel lines and transversals, perpendicular lines, and the angles formed by these...
Key Curriculum Press
Properties of Special Parallelograms
Rhombuses, rectangles and squares are have special properties. In this lesson, young geometers investigate and make conjectures about diagonals, angles, and parallel lines of parallelograms.
Alabama Learning Exchange
Mirror, Mirror on the Wall: Reflections of Light
Why can we see our reflection in a window but not a brick wall? Young physicists learn the Law of Reflection and various light properties that help them answer this and other questions about reflection. Use the PowerPoint to introduce...
EngageNY
Special Lines in Triangles (part 1)
Allow your pupils to become the mathematicians! Individuals explore the properties of a midsegment of a triangle through construction and measurement. Once they figure out the properties, learners use them to draw conclusions.
Curated OER
Determining Angle Measure with Parallel Lines
Young scholars observe and solve examples of corresponding angle postulates, alternate interior angle theorems, and exterior and consecutive angles. They complete the Determining Angle Measure With Parallel Lines worksheet.
EngageNY
Fundamental Theorem of Similarity (FTS)
How do dilated line segments relate? Lead the class in an activity to determine the relationship between line segments and their dilated images. In the fourth section in a unit of 16, pupils discover the dilated line...
EngageNY
Special Lines in Triangles (part 2)
Medians, midsegments, altitudes, oh my! Pupils study the properties of the median of a triangle, initially examining a proof utilizing midsegments to determine the length ratio of a median. They then use the information to find missing...
Curated OER
Similar Situations
Students explore intersecting lines. In this intersecting lines lesson plan, students investigate shapes consisting of parallel, perpendicular, and similar lines. Students investigate these lines in shapes around them.
EngageNY
Definition of Reflection and Basic Properties
Discover the results of reflecting an image. Learners use transparency paper to manipulate an image using a reflection in this fourth lesson of 18. They finish by reflecting various images across both vertical and horizontal lines.
Curated OER
Parallel and Perpendicular Lines
Learners study parallel and perpendicular lines. In this parallel and perpendicular lesson, pupils explore 2-D shapes and determine if the sides are parallel or perpendicular.
Illustrative Mathematics
What Shape Am I?
Sharpen your pencil and grab a ruler, it's time to draw some quadrilaterals! Given the definition of a parallelogram, rectangle, and rhombus, learners draw examples and nonexamples of each figure. The three definitions are...
EngageNY
How Do Dilations Map Angles?
The key to understanding is making connections. Scholars explore angle dilations using properties of parallel lines. At completion, pupils prove that angles of a dilation preserve their original measure.