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Solving Triangles

  • Law of Cosines
  • Law of Sines
  • Law of Tangents

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  • Solving Triangles Lesson Plans
  • Sas
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  • Aas
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Solving Triangles Teacher Resources

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Find Solving Triangles lesson plans and worksheets
Showing 41 resources
Lesson Plan
Introduction to Trigonometric Functions Lesson Plan
West Contra Costa Unified School District

Introduction to Trigonometric Functions

For Teachers 9th - 12th
Scholars first learn the definitions of the sine ratio, the cosine ratio, and the tangent ratio. After mastering these definitions, they use the new information to solve triangles.
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Interactive
Determination of Unknown Triangle Measures Given Area: Jib Sheets Interactive
CK-12 Foundation

Determination of Unknown Triangle Measures Given Area: Jib Sheets

For Students 10th - 12th Standards
Solving triangles is a breeze. Young boat enthusiasts solve problems involving triangles in the context of sails on a boat. They must apply different strategies, including the Law of Cosines and area formulas.
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Worksheet
Leveled Problem Solving  Triangles Worksheet
Curated OER

Leveled Problem Solving Triangles

For Students 4th - 6th
In this triangles practice worksheet, students sharpen their problem solving skills as they solve 6 story problems.
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Worksheet
Using the Law of Sines and the Law of Cosines to Solve Triangles Worksheet
Curated OER

Using the Law of Sines and the Law of Cosines to Solve Triangles

For Students 10th - 12th
In this trigonometry activity, students apply the Law of Sines and Cosines to solving for missing sides of a triangle. There are 5 questions with an answer key.
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Instructional Video4:22
How Do You Solve a Problem Using Indirect Measurement with Shadows? Instructional Video
Curated OER

How Do You Solve a Problem Using Indirect Measurement with Shadows?

For Teachers 6th - 10th
Using indirect measurement, this video shows viewers how to find the height of a flagpole. The lecturer employs drawings as well as proportions to solve this problem, explaining each step. A useful resource to aid struggling learners and...
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Instructional Video4:57
How Do You Solve a Problem Using Indirect Measurement with Shadows? Instructional Video
Curated OER

How Do You Solve a Problem Using Indirect Measurement with Shadows?

For Teachers 6th - 12th
Using indirect measurement, this video shows viewers how to find the height of a flagpole. The lecturer employs drawings as well as proportions to solve this problem, explaining each step. A useful resource to aid struggling learners and...
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Lesson Plan
The Law of Sines and the Law of Cosines Lesson Plan
Curated OER

The Law of Sines and the Law of Cosines

For Teachers Higher Ed
In this college level trigonometry worksheet, students apply the Law of Sines and the Law of Cosines to solve triangles. The four page worksheet contains forty-four problems. Solutions are not provided. 
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Lesson Plan
Triangle Inequality Theorem Lesson Plan
Curated OER

Triangle Inequality Theorem

For Teachers 8th - 10th
Students use the inequality theorem to solve triangles and their properties. In this geometry lesson, students are given spaghetti of different lengths and asked to create triangles. They conclude the necessary length needed to make a...
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Lesson Plan
An Application of Congruence Lesson Plan
Curated OER

An Application of Congruence

For Teachers 9th - 10th
Young scholars solve triangles using the properties if congruency. In this geometry lesson, students apply congruent and similar figures to solve real world and math problems. They show they are able to follow instructions.
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Worksheet
Law of Sines and Law of Cosines Worksheet
Curated OER

Law of Sines and Law of Cosines

For Students 11th - 12th
In this Pre-calculus/Trigonometry worksheet, students use the laws of sines and cosines to solve triangles. The four page worksheet contains thirteen problems. Answers are not included.
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Instructional Video9:27
Proof of the Law of Cosines, Trig Identities and Examples, Trigonometry Instructional Video
Khan Academy

Proof of the Law of Cosines, Trig Identities and Examples, Trigonometry

For Students 11th - Higher Ed
Sal derives the Law of Cosines using a method similar to the wayward ship captain word problem he solves in another video. This video provides a good review of using the SOH-CAH-TOA model, the Pythagorean Theorem, some basic trig...
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Instructional Video6:34
Proof: Law of Sines, Trig Identities and Examples, Trigonometry Instructional Video
Khan Academy

Proof: Law of Sines, Trig Identities and Examples, Trigonometry

For Students 11th - Higher Ed
Sal proves the Law of Sines in this video by using the SOH-CAH-TOA model and setting up equivalent ratios.
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Lesson Plan
The Side-Angle-Side (SAS) and Side-Side-Side (SSS) Criteria for Two Triangles to Be Similar Lesson Plan
EngageNY

The Side-Angle-Side (SAS) and Side-Side-Side (SSS) Criteria for Two Triangles to Be Similar

For Students 9th - 10th Standards
Playing with mathematics can invoke curiosity and excitement. As pupils construct triangles with given criteria, they determine the necessary requirements to support similarity. After determining the criteria, they practice...
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Lesson Plan
The Angle-Angle (AA) Criterion for Two Triangles to Be Similar Lesson Plan
EngageNY

The Angle-Angle (AA) Criterion for Two Triangles to Be Similar

For Teachers 9th - 10th Standards
What do you need to prove triangles are similar? Learners answer this question through a construction exploration. Once they establish the criteria, they use the congruence and proportionality properties of similar objects to find...
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Lesson Plan
Using Trigonometry to Find Side Lengths of an Acute Triangle Lesson Plan
EngageNY

Using Trigonometry to Find Side Lengths of an Acute Triangle

For Students 9th - 10th Standards
Not all triangles are right! Pupils learn to tackle non-right triangles using the Law of Sines and Law of Cosines. After using the two laws, they then apply them to word problems. 
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Lesson Plan
Applying the Laws of Sines and Cosines Lesson Plan
EngageNY

Applying the Laws of Sines and Cosines

For Students 9th - 10th Standards
Breaking the law in math doesn't get you jail time, but it does get you a wrong answer! After developing the Law of Sines and Cosines in lesson 33 of 36, the resource asks learners to apply the laws to different situations. Pupils must...
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Lesson Plan
Sine and Cosine of Complementary Angles and Special Angles Lesson Plan
EngageNY

Sine and Cosine of Complementary Angles and Special Angles

For Students 9th - 10th Standards
Building trigonometric basics here will last a mathematical lifetime. Learners expand on the previous lesson in a 36-part series by examining relationships between the sine and cosine of complementary angles. They also review the...
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Lesson Plan
Algebra 2 & Trigonometry Practice: Law of Sines Lesson Plan
Curated OER

Algebra 2 & Trigonometry Practice: Law of Sines

For Teachers 9th - 12th
In this law of sines worksheet, students solve 9 multiple choice and short answer problems.  Students use the law of sines to missing side lengths and angles of triangles.
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Interactive
Law of Sines or Sine Rule Interactive
Curated OER

Law of Sines or Sine Rule

For Students 9th - 12th
In this online math worksheet, high schoolers construct triangles and squares by utilizing the sine rule. This excellent resource allows the students to check their answers, and to get "hints" should they run into difficulties. A...
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Lesson Plan
Using Trigonometry Lesson Plan
Curated OER

Using Trigonometry

For Teachers 5th
Fifth graders explore the use of trigonometry to find unknown sides and angles in right-angled triangles, taking the concepts that were developed in the previous unit and looking at different ways of practicing the new skills. Students...
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Activity
Math Is Fun: Solving Triangles Activity
Math Is Fun

Math Is Fun: Solving Triangles

For Students 9th - 10th Standards
Find guidelines to help you "solve" triangles, which means finding the value of missing sides and angles. Provided are examples of six scenarios in which you can solve a triangle's missing measurements, as well as relevant equations,...
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Interactive
Learn Alberta: Math Interactives: Exploring and Solving Triangles Interactive
Government of Alberta

Learn Alberta: Math Interactives: Exploring and Solving Triangles

For Students 6th - 8th Standards
This multimedia Learn Alberta math resource focuses on the many triangles that are found in our everyday environment. The accompanying interactive component asks students to find triangles in a picture and to solve for the missing angles...
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Activity
Trig Without Tears: Solving Triangles Activity
Other

Trig Without Tears: Solving Triangles

For Students 9th - 10th Standards
This page provides a good explanation of how to solve oblique triangles (triangles containing no right angles.) The Law of Cosines section is about halfway of the way down the page.
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Unknown Type
Khan Academy: Solve Triangles Using the Law of Cosines Unknown Type
Khan Academy

Khan Academy: Solve Triangles Using the Law of Cosines

For Students 9th - 10th Standards
Solve missing triangle measures using the law of cosines. Students receive immediate feedback and have the opportunity to try questions repeatedly, watch a video or receive hints.
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