PPT
Sophia Learning

Sophia: Triangle Interior Angles Practice: Lesson 1

For Students 9th - 10th
This lesson provides practice problems that involve the sum of the interior angles of triangles. It is 1 of 6 in the series titled "Triangle Interior Angles Practice."
Lesson Plan
Illustrative Mathematics

Illustrative Mathematics: F Tf Sum and Difference Angle Formulas

For Teachers 9th - 10th Standards
The goal of this task is to have students derive the addition and subtraction formulas for cosine and tangent, and the subtraction formula for cosine, from the sum formula for sine. Aligns with F-TF.C.9.
Handout
Free Math Help

Free Math Help: Exterior Angle of a Triangle

For Students 7th - 8th Standards
This tutorial discusses exterior angles of a triangle. Example problems with explanations are included.
Activity
AAA Math

Aaa Math: Finding the Third Angle of a Triangle

For Students 9th - 10th Standards
Finding the third angle of a triangle becomes easier by the explanation and examples presented.
Activity
Free Math Help

Free Math Help: Angles of a Triangle Sum

For Students 9th - 10th
The lesson discusses the angle-sum theorem. The resource consists of an explanation and practice problems with solutions.
Activity
National Council of Teachers of Mathematics

The Math Forum: Problems Library Geometry Triangles

For Students 9th - 10th Standards
This site contains a wealth of problems that deal with the basic definitions of medians, altitudes, angle bisectors, and perpendicular bisectors or the defining characteristics of the different types of triangles. There are also...
Handout
CK-12 Foundation

Ck 12: Geometry: Triangle Relationships Study Guide

For Students 9th - 10th Standards
[Free Registration/Login may be required to access all resource tools.] This study guide reviews terminology for triangles, triangle properties, different types of triangles, and interior and exterior angle theorems.
Activity
Texas Instruments

Texas Instruments: Measuring Polygons an Introduction to Cabri Jr.

For Teachers 9th - 10th
This activity is designed as an introduction to using the Carbri Jr. application on the TI-83+/84+ calculators. Students are guided through the menu system and are shown how to draw triangles, quadrilaterals and and a pentagon. Perimeter...
Activity
Varsity Tutors

Varsity Tutors: Hotmath: Graphing Calculator Practice Problems Geometry

For Students 9th - 10th Standards
Practice using your graphing calculator for Geometry problems. If you get stumped or if you would like to check your work, then select the View Solution button, which is located directly under each problem.
Activity
Windstream

Ojk's Precalculus Study Page: Double and Half Angle Formulas

For Students 9th - 10th Standards
This tutorial introduces the double-angle and half-angle formulas for sine, cosine, and tangent, and gives sample application and proof exercises. Assumes knowledge of the sum and difference formulas.
Unit Plan
Texas Education Agency

Texas Gateway: Making and Verifying Conjectures About Triangles

For Students 9th - 10th
Given examples of triangles and their component parts, the student will use explorations and concrete models to verify and apply the and find the sum of interior angles.
Activity
Math Medics

S.o.s. Math: Table of Trigonometric Identities

For Students 9th - 10th Standards
This tutorial highlights the numerous trigonometric identites (but does not define the basic trigonometric functions).
Whiteboard
ClassFlow

Class Flow: Investigating Regular Polygons

For Teachers 9th - 10th
[Free Registration/Login Required] In this lesson students are introduced to regular polygons. Students learn how to find the drawing angle of any given polygon, exterior angle, interior angle and the sum of the angles for a regular...
Unit Plan
Texas Education Agency

Texas Gateway: Writing Geometric Relationships

For Students 7th - 9th Standards
Given information in a geometric context, students will be able to use informal arguments to establish facts about the angle sum and exterior angle of triangles, the angles created when parallel lines are cut by a transversal, and the...
Activity
Homeschool Math

Homeschool Math: Equilateral, Isosceles, and Scalene Triangles

For Students 4th - 6th
This geometry lesson defines equilateral, isosceles, and scalene triangles, and has a variety of exercises, including drawing exercises.
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)
Activity
Math Words

Math words.com: Trig Identities

For Students 9th - 10th Standards
This MathWords.com site lists the equations for all of the trigonometric identities.
Activity
Other

Brown Math: Remembering Trig Identities

For Students 9th - 10th Standards
Faced with a large number of trigonometric identities, students tend to try to memorize them all. This site the emphasis is on understanding how the functions work and on memorizing only about a half dozen of them - all the others work...
Activity
Lawrence Hall of Science

The Math Page: Trigonometry: Trigonometric Identities

For Students 9th - 10th Standards
This resource clearly and thoroughly explains the many types of trigonometric identities. There are example problems solved, problems for the student to attempt, and answers to the student problems.
Interactive
Walter Fendt

Walter Fendt: Cyclic Quadrilateral (Inscribed Quadrilateral)

For Students 9th - 10th Standards
A short interactive activity which allows you to move the vertices of a quadrilateral to prove that the sum of the opposite angles is 180 degrees.
Unit Plan
Cuemath

Cuemath: Obtuse Triangle

For Students 9th - 10th Standards
In this mini-lesson, learn about obtuse triangles including the obtuse triangle definition, sides, properties, examples, and other fun facts related to it.
Unit Plan
Cuemath

Cuemath: Triangles

For Students 5th - 8th Standards
Explore everything about triangles. Learn about the different types, important properties, and how to find its area and perimeter. Check out the solved examples and interactive questions for better understanding.

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