Handout
CK-12 Foundation

Ck 12: Geometry: Special Right Triangles Study Guide

For Students 9th - 10th Standards
[Free Registration/Login may be required to access all resource tools.] Different types of right triangles and trigonometric ratios for special right triangles are covered in this study guide.
Unit Plan
CK-12 Foundation

Ck 12: Trigonometry: Lengths of Sides in Isosceles Right Triangles

For Students 10th - 12th Standards
[Free Registration/Login may be required to access all resource tools.] Here you'll learn what an isosceles right triangle is, the relationships between the sides of an isosceles right triangle, and how to find the length of an unknown...
eBook
CK-12 Foundation

Ck 12: Algebra Ii: 4.2 Right Triangle Trig Extended to Circles With a Model

For Students 9th - 10th Standards
This section explores the relationship between right triangles, circles, and trigonometry. It investigates how a right triangle that is set inside a circle and rotates around the circle is connected to trigonometric functions and their...
eBook
Mathigon

Mathigon: Geometry: Triangles and Trigonometry: Properties of Triangles

For Students 9th - 10th Standards
This lesson focuses on the properties of triangles, a closed shape that has three sides, three vertices, and and three internal angles. There are different types of triangles such as a right triangle, obtuse, and acute based on the...
Activity
Shodor Education Foundation

Shodor Interactivate: Triangle Explorer

For Students 9th - 10th Standards
This applet allows users to study the nature of triangles and their area. It draws random triangles on a Cartesian coordinate system. The user can determine the area of the triangle using his or her preferred method. After the calculated...
Unit Plan
Cuemath

Cuemath: Altitude of a Triangle

For Students 9th - 10th Standards
Explore the world of the altitude of a triangle in this mini-lesson including its definition, altitudes in different types of triangles, formulae, some solved examples, and a few interactive questions for you to test your understanding.
Unit Plan
Oswego City School District

Regents Exam Prep Center: Area of a Triangle and Parallelogram Using Trig

For Students 9th - 10th Standards
How can trigonometry be used to find the area of a triangle or parallelogram? Does the triangle need to be a right triangle, and how accurate can the results possibly be? The answers to these questions are found here along with several...
Lesson Plan
Illustrative Mathematics

Illustrative Mathematics: G Co Classifying Triangles

For Teachers 9th - 10th Standards
The goal of this task is to help students synthesize their knowledge of triangles where only two of the vertices have been given. They will need to know that a triangle inscribed in a circle, with a diameter of the circle as one side, is...
Lesson Plan
Science Buddies

Science Buddies: Gigantic Triangles: Measuring Altitude (Inclinometer)

For Teachers 6th - 8th
If you've ever wondered how tall that bridge is, or how high your kite was, then this could be a good project for you. You'll learn how you can use the mathematics of right triangles to measure the height of an object with two...
Lesson Plan
Illustrative Mathematics

Illustrative Mathematics: F Tf Equilateral Triangles and Trigonometric Functions

For Teachers 9th - 10th Standards
The purpose of this task is to apply knowledge about triangles to calculate the sine and cosine of 30 and 60 degrees. Aligns with HSF-TF.A.3.
Handout
Math Open Reference

Math Open Reference: Circumcircle of a Triangle

For Students 9th - 10th Standards
A complete reference guide to the circumcircle of a triangle. It provides definitions, examples, and an interactive activity that enhances further explanation. Includes links to related topics.
Unit Plan
CK-12 Foundation

Ck 12: Determination of Unknown Triangle Measures Given Area

For Students 10th - 12th Standards
[Free Registration/Login may be required to access all resource tools.] Looks at triangle problems where you are given the area and must use trigonometry to find unknown sides or angles.
eBook
CK-12 Foundation

Ck 12: Algebra Ii: 4.1 Revisiting Right Triangle Trigonometry

For Students 9th - 10th Standards
Use this tutorial to revisit right triangle trigonometry.
Handout
Purple Math

Purplemath: Special Angle Values: 30 60 90 and 45 45 90 Triangles

For Students 9th - 10th
Explains a simple pictorial way to remember basic reference angle values. Provides other memory aids for the values of trigonometric ratios for these "special" angle values, based on 30-60-90 triangles and 45-45-90 triangles.
Handout
Math Open Reference

Math Open Reference: The Circumcenter of a Triangle

For Students 9th - 10th
Learn about the circumcenter of a triangle with this handy reference guide. Provides a detailed definition, examples, and an interactive activity that enhances further explanation. Includes links to related topics.
Activity
Shodor Education Foundation

Shodor Interactivate: Interactive: Pythagorean Explorer

For Students 6th - 8th Standards
Students find the length of a side of a right triangle by using the Pythagorean Theorem and then check their answers.
eBook
CK-12 Foundation

Ck 12: Algebra Ii: 4.8 Pythagorean Identities

For Students 9th - 10th Standards
This section explores the Pythagorean Identity and how it applies to right triangles set inside unit circles, in terms of sine, cosine, and tangent functions.
Interactive
Shodor Education Foundation

Shodor Interactivate: Squaring the Triangle

For Students 9th - 10th Standards
Learn about how the Pythagorean Theorem works through investigating the standard geometric proof.
Handout
Math Is Fun

Math Is Fun: Area of Triangles Without Right Angles

For Students 9th - 10th Standards
Learn how to find the area of triangles without right angles. Find the formula to use depending on the information you know about the triangle: base and height, three sides, or two sides and an angle.
eBook
Mathigon

Mathigon: Geometry: Triangles and Trigonometry: Pythagoras' Theorem

For Students 9th - 10th Standards
Pythagoras' Theorem: In any right-angled triangle, the square of the length of the hypotenuse (the side that lies opposite the right angle) is equal to the sum of the squares of the other two sides. (A+B=C)
eBook
CK-12 Foundation

Ck 12: Algebra Ii: 1.10 Pythagorean Triples

For Students 9th - 10th
This section explores right triangles with three lengths that are considered Pythagorean Triples, and also investigates how some right triangles can have lengths that are not Pythagorean Triples.
Interactive
Shodor Education Foundation

Shodor Interactivate: Pythagorean Explorer

For Students 9th - 10th Standards
Calculate the length of one side of an automatically generated right triangle by using the Pythagorean Theorem, and then check your answers.
Article
Mocomi & Anibrain Digital Technologies

Mocomi: Types of Triangles

For Students 2nd - 8th Standards
Explore the different types of triangles and other properties.
Interactive
Doina Popovici

Math Play: Pythagorean Theorem Jeopardy Game

For Students 6th - 9th Standards
This jeopardy-style game will have students calculate the sides of a right triangle by using the Pythagorean Theorem.

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