# Geometric Proof Teacher Resources

Find Geometric Proof lesson plans and worksheets
Showing 73 - 96 of 152 resources
Lesson Planet

#### Congruent Triangles Applications

For Students 9th - 12th Standards
Triangles are all about threes, and practicing proving postulates is a great way to get started. The first page of the worksheet provides a brief introduction of the different properties and postulates. The remaining pages contain...
Lesson Planet

#### Converse of the Triangle Proportionality Theorem

For Students 9th - 12th Standards
They say the proof is in the pudding ... hopefully, in this case, the theorem isn't in there as well! Learners tackle the task of explaining the relationships between segments within a triangle. The assessment is designed to demonstrate...
Lesson Planet

#### Justifying SAS Congruence

For Students 9th - 12th Standards
Triangle congruence is based upon rigid transformations. Given two triangles with congruent corresponding side-angle-side relationships, pupils provide a detailed description of why the two triangles must be congruent. The scholars use...
Lesson Planet

#### Justifying HL Congruence

For Students 9th - 12th Standards
What is so special about right triangle congruence? Pupils use what they know about transformations and right triangles to develop a proof of hypotenuse-leg congruence. The proof provides the given of two angles that measure 90 degrees...
4:01
Lesson Planet

#### Classifying Parallelograms: Lesson

For Students 8th - 11th Standards
Properly organize parallelograms. Given special parallelograms, the narrator of a short video explains the properties of each. The section of a playlist on geometry uses the properties to classify the special parallelograms.
Lesson Planet

#### Angles and Sides, Sides and Angles

For Teachers 10th - 12th Standards
Lead by example. Pupils use software to investigate given measures of sides and angles to determine whether they create congruent triangles. Using the discovered triangle congruences, learners put together proofs.
2 In 2 Collections
Lesson Planet

#### Are They Similar?

For Teachers 9th - 11th Standards
Learners separate things that just appear similar from those that are actually similar. A diagram of triangles is given, and then a variety of geometric characteristics changed and the similarity of the triangles analyzed. Because the...
Lesson Planet

#### Rhombuses

For Teachers 9th - 12th Standards
Just what does it take to show two rhombuses are similar? The assessment task asks pupils to develop an argument to show that given quadrilaterals are rhombuses. Class members also use their knowledge of similar triangles to show two...
EngageNY

#### Special Lines in Triangles (part 2)

For Teachers 9th - 10th Standards
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...
EngageNY

#### Congruence Criteria for Triangles—SAS

For Students 9th - 10th Standards
Looking for a different approach to triangle congruence criteria? Employ transformations to determine congruent triangles. Learners list the transformations required to map one triangle to the next. They learn to identify congruence if...
Lesson Planet

#### An Isosceles Trapezoid Problem

For Students 9th - 12th Standards
Prove the diagonals are shorter than the perimeter. Given an isosceles trapezoid, pupils develop a proof relating the length of the diagonals to the perimeter. Individuals sketch a graph of the trapezoid to assist with their explanations.
Lesson Planet

#### Equidistant Points

For Students 9th - 12th Standards
What's so special about perpendicular bisectors? Pupils investigate points on the perpendicular bisector of a line segment. They write a proof for why a point on the perpendicular bisector is equidistant from the endpoints of the line...
Lesson Planet

#### Justifying SSS Congruence

For Students 9th - 12th Standards
Are congruent corresponding sides of two triangles enough to show congruence? The short assessment provides two triangles with the information that the three sets of corresponding sides are congruent. Pupils develop a proof showing that...
EngageNY

#### End-of-Module Assessment Task - Geometry (module 1)

For Students 9th - 10th Standards
Have you hit a wall when trying to create performance task questions? Several open-ended response questions require a deep level of thinking. Topics include triangle congruence, quadrilaterals, special segments, constructions, and...
Lesson Planet

#### Isosceles Triangles and Special Line Segments

For Students 9th - 12th Standards
Under which conditions can a triangle be classified as isosceles? High schoolers practice identifying isosceles triangles and special line segments, including angle bisectors, medians of triangles, and perpendicular bisectors of sides of...
Lesson Planet

#### Pythagorean Theorem

For Students 8th Standards
Investigate the meaning of the Pythagorean Theorem through modeling. After comparing the area of the square of each side, individuals cut triangles and squares to facilitate the comparison.
Lesson Planet

#### Area and Circumference 2

For Students 9th - 12th Standards
Use scale factors to find areas of circles. Pupils delve deeper into the informal argument for the formula of the area of a circle. The scholars show the relationships of areas of similar polygons also holds true for circles.
Lesson Planet

#### Midpoints of Sides of a Quadrilateral

For Students 9th - 12th Standards
Verify a figure by using coordinates. Pupils calculate the coordinates of the midpoints of the sides of a quadrilateral. They then use the coordinates to show the resulting figure is a parallelogram.
EngageNY

#### Review of the Assumptions (part 2)

For Students 9th - 10th Standards
Is the amount of information getting overwhelming for your geometry classes? Use this strategy as a way to organize information. The resource provides a handout of information studied in relation to triangle congruence. It includes a...
Lesson Planet

#### Diagonals of a Rectangle

For Students 9th - 12th Standards
Coordinate the vertices of a rectangle. Pupils use the location of three vertices of a rectangle along the axis to find the coordinates of the fourth vertex. Using the vertices of the rectangle, scholars prove the diagonals are congruent...
EngageNY

#### Scale Factors

For Students 9th - 10th Standards
Is it bigger, or is it smaller—or maybe it's the same size? Individuals learn to describe enlargements and reductions and quantify the result. Lesson five in the series connects the creation of a dilated image to the result. Pupils...
3:58
Lesson Planet

#### Triangle Angle Sum

For Students 9th - 12th Standards
Don't believe everything that you hear — make them prove it! The video shows two methods to prove the Triangle Angle Sum Theorem. The following two videos apply the theorem to finding missing angle measures.
Lesson Planet

#### Square

For Students 8th - 12th Standards
Don't be a square! Young mathematicians determine the slope and length of a line segment. They then prove whether four given coordinate points form a square.
EngageNY

#### Looking More Carefully at Parallel Lines

For Students 9th - 10th Standards
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...