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Unit Plan
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Mathematics Vision Project

Similarity and Right Triangle Trigonometry

For Teachers 10th - 12th Standards
Starting with similar triangles and dilation factors, this unit quickly and thoroughly progresses into the world of right triangle features and trigonometric relationships. Presented in easy-to-attack modules with copious application...
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Lesson Plan
EngageNY

Solve for Unknown Angles—Transversals

For Teachers 9th - 10th Standards
Lead your class on an exciting journey through the world of math as they review geometry facts and solve for unknown angles. They learn how to use auxiliary lines and congruent angles to correctly complete each practice problem...
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Worksheet
Curated OER

Proofs with Triangles

For Students 9th - 12th
For this geometry worksheet, students prove triangle congruence by making statements with reasons and concluding with the AAS or HL theorem. There are 2 proofs.
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Worksheet
Curated OER

Logical Relationship of Postulates & Theorems

For Students 10th - 12th
In this postulates and theorems learning exercise, students explore a concept map containing information about angles and sides, alternate interior angles, and diagonals of a parallelogram.  They use the concept map to prove theorems...
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Lesson Plan
Curated OER

Exploring Characteristics Needed to Prove Two Trianlges Congruent

For Teachers 10th
Tenth graders explore congruent triangles.  In this geometry lesson, 10th graders investigate the conditions necessary to prove two triangles congruent.  The lesson combines dry erase board activities and the use of technology.
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Lesson Plan
Illustrative Mathematics

Joining Two Midpoints of Sides of a Triangle

For Teachers 9th - 11th Standards
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 lines cut...
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Lesson Plan
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Curated OER

A Rectangle in the Coordinate Plane

For Teachers 7th - 9th Standards
A quadrilateral is drawn on the coordinate plane, and eighth grade geometers find the length of each side and the diagonals by applying the Pythagorean theorem. 
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Worksheet
Curated OER

Eighteen SSS or SAS Triangle Congruence Problems

For Students 9th - 10th
In this triangle congruence worksheet, students state if triangles are congruent and if the congruence is based on side, side, side or the side, angle, side theorems in eighteen problems.  The solutions are found on the last two pages.
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Lesson Plan
Curated OER

Similar triangles

For Teachers 10th
Tenth graders investigate the theorems of ASA, AAS, AAA and ASA. In this geometry lesson plan, 10th graders discuss the theorems of triangles and how it is used to solve for missing sides or angles. They review how two angles are formed...
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Worksheet
Curated OER

Geometry: Angles

For Students 11th - 12th
In this angle worksheet, students find the value for a given variable. They use similar figures, alternate interior angles, side angle side, and other geometric theorems and proofs to determine the value of the given variable. This...
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Worksheet
Curated OER

Congruent Triangles

For Students 10th
In this congruent triangles instructional activity, 10th graders solve and complete 16 different types of problems. First, they name the corresponding parts of the congruent triangles shown and draw a picture. Then, students list the...
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Worksheet
Curated OER

More Congruent Triangles

For Students 10th
In this congruent triangles instructional activity, 10th graders solve 6 various forms of problems that include a proof and a word problem. First, they draw and label triangles and indicate the additional pairs of corresponding parts...
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Worksheet
Curated OER

Quiz: Geometric Constructions-Congruence

For Students Higher Ed
In this congruent figures worksheet, students answer ten true or false questions. A sample question reads: "Two triangles are congruent when their shape and size will be the same."
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Lesson Plan
Curated OER

Congruent Triangles Postulates

For Teachers 3rd - 4th
Students discover three lettered postulates that prove triangles congruent.
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Lesson Plan
EngageNY

More About Similar Triangles

For Teachers 8th Standards
Determine whether two triangles are similar. The lesson presents opportunities for pupils to find the criterion needed to show that two triangles are similar. Scholars use the definition of similarity to find any missing side...
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Assessment
Inside Mathematics

Hopewell Geometry

For Teachers 9th - 12th Standards
The Hopewell people of the central Ohio Valley used right triangles in the construction of earthworks. Pupils use the Pythagorean Theorem to determine missing dimensions of right triangles used by the Hopewell people. The assessment task...
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Lesson Plan
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Illustrative Mathematics

Right Triangles Inscribed in Circles I

For Teachers 9th - 10th Standards
One of the basic properties of inscribed angles gets a triangle proof treatment in a short but detailed exercise. Leading directions take the learner through identifying characteristics of a circle and how they relate to angles and...
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Lesson Plan
Curated OER

Angles and Similarity

For Teachers 9th - 12th Standards
Students identify triangles as similar or congruent. In this geometry lesson plan, students drag triangles around on the navigator to see the effect of different angles on the shape of the triangle. They discuss angle similarity and...
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Lesson Plan
Curated OER

Analyzing Body Angles

For Teachers 10th - 12th
Students investigate angles of polygons. In this geometry lesson, students identify the relationship between angles and the number of sides in a polygon. They differentiate between sumilarity anf congruence in angles and sides.
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Worksheet
Curated OER

More Congruent Triangles

For Students 10th
In this congruent triangles worksheet, 10th graders solve 5 various types of geometry problems related to triangles. First, they draw and label triangles, indicating the additional pairs of corresponding parts that would have to be...
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Worksheet
Curated OER

Proving Triangles Congruent

For Students 10th
In this proving triangles congruent worksheet, 10th graders solve 5 different problems that include proofs and proving congruence in triangles. First, they determine which postulate can be used to prove the triangles congruent and mark...
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Lesson Plan
Curated OER

Pythagorean Theorem

For Teachers All
Students explore how the Pythagorean Theorem works and how to apply it.
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Lesson Plan
Curated OER

Pythagorean Theorem

For Teachers 9th - 12th
Young scholars are introduced to the Pythagorean theorem. They use three different activities that give students the opportuntiy to observe triangles, and use the Pythagorean theorem and practice different ways of determining areas of...
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Lesson Plan
EngageNY

Law of Sines

For Teachers 11th - 12th Standards
Prove the Law of Sines two ways. The ninth segment in a series of 16 introduces the Law of Sines to help the class find lengths of sides in oblique triangles. Pupils develop a proof of the Law of Sines by drawing an altitude and a second...