Transform the thinking of transformations with six sample items that illustrate the first four standards in the eighth grade geometry domain. Items use the coordinate plane to transform figures and analyze the relationship of the figures...

Look at dilations exponentially. Using a fractal from a museum exhibit, the installment from the Math at the Core: Ratios series introduces the term dilation. The presenter points out that dilations can make images either smaller or...

Explore angle relationships with a hands-on activity. Young mathematicians begin by drawing parallel lines cut by a transversal and measuring the angle pairs. After establishing the angle pairs, individuals show their understanding by...

If two sets of angles are equal, the third set is too. An informative portion of a playlist on geometry develops the Third Angle Theorem for triangles. Using the theorem, the presenter shows how to determine the measure of missing angles...

Using the definition of a trapezoid, the segment within a large playlist on basic geometry explains other properties of trapezoids. The video introduces the special properties held by isosceles trapezoids.

How is congruence shown? Using angles, the resource introduces the congruence symbol and explains the meaning of being congruent. A segment of a larger playlist on basic geometry discusses bisection as a way to arrive at two congruent...

Applying their knowledge of theorems about lines, angles, and triangles, groups build a toothpick and stick bridge to support their text book. The teams use the design process to plan, build, test, and refine their bridge designs. The...

Examine similarity through a lens of transformations. A creative question asks learners to explain the properties of the angles and sides of similar figures. They must use the definition of transformations to build their explanations.

Transform proofs using triangle rotations. By rotating a triangle around various points, class members develop proofs. Participants prove relationships of alternative interior angles formed by parallel lines and the sum of the interior...

Translate, reflect, and rotate one triangle onto another. Given two triangles with corresponding parts, individuals use properties of rigid transformations to show the two triangles are congruent. Pupils show that after a series of...

Transform a diagram into a proof. Given two triangles on a coordinate plane, pupils develop a proof to show they are similar. The learners use the fact that two angles of one triangle are congruent to two angles of another and their...

No two resources are exactly the same, but polygons can be. Scholars match congruent figures by dragging them together in an interactive. They answer some challenge questions that justify their matches.

Don't let congruent figures drag you down. Young mathematicians use an interactive to drag figures onto one another to determine if the figures are congruent.

Proofs not included; you must write them on you own. Learners write a proof that alternate interior angles are congruent. The proof must rely on rigid motions.

Opposite angles in a parallelogram aren't opposites, so what are they? Scholars prove that opposite angles of a parallelogram are congruent. A two-column proof might be appropriate here.

Isosceles means two sides are congruent. Given an isosceles triangles, pupils develop a geometric proof showing that the two base angles are congruent. 

Who doesn't like pizza?  A creative lesson uses a piece of pizza to explore angle bisectors and congruent angles. Young scholars work through a simulation to create congruent slices of pizza by analyzing an angle bisector. They then...

How does your class measure up to finding angle measurements? Young scholars of geometry find the measurements of four missing angles on three concurrent lines. After finding each measurement, they must then justify their answers. Use...

Can your pupils determine the measurement of seven angles from the measurement of just one? Geometry enthusiasts tackle this task in a problem involving parallel lines with a transversal. After finding the correct measurements, the class...

Are pupils prepared for the perfect parallelogram problem? Let them put their skills to the test using a formative assessment that's short and focused. Geometry scholars sketch a parallelogram and find the measure of an angle, then...

Is your class confounded by congruency? Find out using a fast, fun formative assessment. Learners must construct a congruent angle using the proper tools, then explain their thought processes. The included rubric contains information to...

Congruent figures: two figures that want to be just like each other. Individuals learn to distinguish between figures that are congruent and those that are not. Measuring the lengths of line segments and angles helps in this endeavor.

Is this enough to show the two triangles are congruent? Small groups work through different combinations of constructing triangles from congruent parts to determine which combinations create only congruent triangles. Participants use the...

Explore angle relationships associated with transversals. Pupils construct parallel lines with a transversal and find the measures of the angles formed. They figure out how the different angles are related before constructing...