Can you prove it? Making assumptions in geometry is commonplace. This resource requires mathematicians to prove the parallel line postulate through constructions. Learners construct parallel lines with a 180-degree rotation and then...

Use the alphabet as a tool for teaching your class about geometric figures. Break apart capital letters into line segments and arcs. Classify angles as right, acute, or obtuse. Identify parallel and perpendicular lines. An excellent...

How do you fit a tape measure around the Earth? No need if you know a little geometry! Pupils begin by extending their understanding of the Side Splitter Theorem to a transversal cut by parallel lines. Once they identify the...

Use what you know about parallel and perpendicular lines to write equations! Learners take an equation of a line and write an equation of a line that is parallel or perpendicular using slope criteria. They then solve problems to...

Get jamming with lines and sing along to this karaoke that reviews the main types of lines. Your learners can't forget the main properties of lines when they sing the chorus on the karaoke song after the included slide show. The slides...

Streets, bridges, and intersections, oh my! Parallel lines and transversals are a present in the world around us. Learners begin by discovering the relationship of the angles formed by parallel lines and a transversal. They then...

The coordinate plane links key geometry and algebra concepts in this approachable but rigorous unit. The class starts by developing the distance formula from the Pythagorean Theorem, then moves to applications of slope. Activities...

Why was the obtuse angle upset? Because it was never right! A valuable resource is loaded with background information on types of angles and lines. Learners review the characteristics of parallel, perpendicular, and...

A geometry module connects algebraic reasoning to geometry. It challenges scholars to investigate the slope criteria for parallel and perpendicular lines, prove theorems involving coordinate geometry, and write equations for circles and...

We can mathematically model the path of a robot. Learners use parametric equations to find the location of a robot at a given time. They compare the paths of multiple robots looking for parallel and perpendicular relationships and...

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...

You've investigated relationships between chords, radii, and diameters—now it's time for arcs. Learners investigate relationships between arcs and chords. Learners then prove that congruent chords have congruent arcs, congruent arcs have...

How many ways can you create a dilation? Many! Individuals strengthen their understanding of dilations by using various methods to create them. The new technique builds on pupils' understanding of the ratio method. Using the ratio,...

More than a activity, learners go through geometry topics example by example on the nicely organized handout. From postulates to classifying angles, there are rules and examples provided for each topic. The ten pages of problems...

Can you prove it? Lead your class through the development of the Side Splitter Theorem through proofs. Individuals connect the ratio and parallel method of dilation through an exploration of two proofs. After completing the proofs,...

Geometry meets earth science as high schoolers investigate the cause and features of the four seasons. The effects of Earth's axis tilt features prominently, along with both the rotation of the earth about the axis and its orbit...

This amazingly extensive unit covers a wealth of geometric ground, ranging from constructions to angle properties, triangle theorems, rigid transformations, and fundamentals of formal proofs.  Each of the almost-forty lessons...

Your learners connect the new concepts of transformations in the coordinate plane to their previous knowledge using the solid vocabulary development in this unit. Like a foreign language, mathematics has its own set of vocabulary terms...

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.

Trace the links between a variety of math concepts in this far-reaching unit. Ideas that seem very different on the outset (like the distance formula and rigid transformations) come together in very natural and logical ways. This...

Learn through constructions! Learners examine a translation using constructions and define the translation using a vector. Pupils then construct parallel lines to determine the location of a translated image and use the vector as a guide.

Your learners combine their knowledge of real and imaginary numbers and matrices in an activity containing thirty lessons, two assessments (mid-module and end module), and their corresponding rubrics. Centered on complex numbers and...

Face the vertex of two-dimensional shapes and discover what each figure requires as part of its classification. With one shape per slide, learners see what makes each shape special and compare it to others with similar qualities. 

Given a pair of parallel lines and a triangle in between, geometers prove that the sum of the interior angles is 180 degrees. This quick quest can be used as a pop quiz or exit ticket for your geometry class.