Curated OER
Which Quadrilateral Is It?
Students prove conjectures about geometric figures on the plane or in space using coordinate geometry. They develop fluency in operations with real numbers, vectors and matrices using mental computation or paper-and-pencil calculations...
EngageNY
Informal Proof of AA Criterion for Similarity
What does it take to show two triangles are similar? The 11th segment in a series of 16 introduces the AA Criterion for Similarity. A discussion provides an informal proof of the theorem. Exercises and problems require scholars to apply...
Curated OER
Where in the World
Students explore the global grid system. In this globe lesson, students identify latitude and longitude lines and how these can tell the coordinates of any place. They use the Internet to find the exact coordinates for their town.
West Contra Costa Unified School District
Investigating Similar Triangles
Let your use of the resource be in proportion to its usefulness. Pupils investigate similar triangles by measuring side lengths and considering given angle measures. The results of the investigation help develop generalizations about...
West Contra Costa Unified School District
Investigating Special Right Triangles
Scholars first investigate relationships in the side lengths of 30°-60°-90° triangles and 45°-45°-90° triangles. This knowledge then helps them solve problems later in the lesson plan about special right triangles.
EngageNY
Congruence Criteria for Triangles—SAS
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...
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
SAS Similarity Theorem
Students identify and use the similarity theorem. In this geometry lesson, students differentiate between congruent and similar triangles. They solve problems using the computer modifying shapes by dragging.
Curated OER
Application of Properties of Quadrilaterals in the Coordinate Plane
Learners apply definitions and theorems to verify special quadrilaterals
using coordinate geometry. They apply the slope formula, the midpoint
formula, and the distance formula to justify that a given quadrilateral is a
parallelogram....
Curated OER
Walking Down Main Street: The Changing Times of a Railroad Town
Students explore the historic district via a scavenger hunt. In this community history lesson, students complete a scavenger hunt using historic postcards and clues as guides. Students create a timeline demonstrating changes of the area...
Curated OER
Polygons All Around Us!
Students explore the concept of polygon properties. In this polygon properties lesson plan, students draw polygons with different numbers of sides such as pentagons, octagons, hexagons, etc. Students identify different geometric shapes...
Illustrative Mathematics
Illustrative Mathematics: G Gpe Parallel Lines in the Coordinate Plane
The goal of this task is to prove the slope criterion for parallel lines. Aligns with HSG-GPE.B.5.
Illustrative Mathematics
Illustrative Mathematics: G Srt Joining Two Midpoints of Sides of a Triangle
In this task, students must prove that angles and triangles are congruent and that a parallel line passes through the midpoints of two sides of the larger triangle. Aligns with G-SRT.B.4.
Illustrative Mathematics
Illustrative Mathematics: 8.g.a Triangle's Interior Angles
In this task, 8th graders are presented with a drawing of two parallel lines with a triangle touching them at all three of its vertices. They are asked to prove that the sum of the triangles' angles equals 180 degrees. Aligns with 8.G.A.5.
Illustrative Mathematics
Illustrative Mathematics: G Gpe a Midpoint Miracle
In this task, students are asked to draw a quadrilateral so that no two sides are congruent, no two angles are congruent, and no two sides are parallel. The task gives students the opportunity to prove that if we join the midpoints of a...
Illustrative Mathematics
Illustrative Mathematics: G Gpe, G Co, G Srt Unit Squares and Triangles
In this task, students are shown three unit squares and two line segments connecting two pairs of vertices. They are asked to find the area of a triangle formed by intersecting lines. They can solve it using coordinate geometry or...
Illustrative Mathematics
Illustrative Mathematics: G Gpe.5 Triangles Inscribed in Circle
In this task, students use ideas about linear functions to determine when certain angles are right angles. They use the fact that two lines (if not vertical or horizontal) are perpendicular when their slopes are inverse reciprocals, as...
Illustrative Mathematics
Illustrative Mathematics: G Co Midpoints of the Sides of a Paralellogram
Suppose that ABCD is a parallelogram and that M and N are the midpoints of lines AB and CD respectively. Students are asked to prove that MN=AD, and that the line MN is parallel to line AD. Aligns with G-CO.C.11.