Walter Fendt
Walter Fendt: Sum of Angles in a Triangle
A short interactive activity to show that the sum of the angles of a triangle is 180 degrees.
Illustrative Mathematics
Illustrative Mathematics: F Tf Sum and Difference Angle Formulas
The goal of this task is to have learners 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.
Texas Instruments
Texas Instruments: Measuring Angles in a Quadrilateral
In this activity, use an interactive, and investigative approach to determining the sum of the interior angles of a quadrilateral. They use Cabri Jr. to draw, measure, and calculate the characteristics of the angles of quadrilaterals.
Texas Instruments
Texas Instruments: Measuring Angles in a Triangle
In this activity, students learn about the sum of the angles in a triangle. They understand triangles and their interior angles.
Mangahigh
Mangahigh: Shape: Proof of the Sum of the Angles in a Triangle
Determine that all angles in a triangle equal 180 degrees.
Texas Instruments
Texas Instruments: Betweenness and the Sum of Parts
In this activity, students will explore the concepts of betweenness and the sum of parts visually, geometrically, and numerically for segments and angles using the Cabri Jr. application. They will investigate how the sum of parts equals...
Texas Instruments
Texas Instruments: Triangle Sum
This activity is used to discover that the sum of the measures of the triangle angles is constant and to discover ways of proving the theorem listed in the activity.
Mangahigh
Mangahigh: Shape: The Angles Inside a Quadrilateral
Test your knowledge of the sum of angles inside a quadrilateral.
Mangahigh
Mangahigh: Shape: Interior Angles of Polygons
Determine the sum of the interior angles of polygons.
Mathigon
Mathigon: Geometry: Angles and Polygons: Drawing Triangles
This lesson focuses on the Triangle Inequality, when the sum of the lengths of any two sides of a triangle is greater than the length of the third. When this happens, the three sides cannot form a triangle.
Oswego City School District
Regents Exam Prep Center: Exterior Angles of Polygons
This site explains what the measure of the sum of exterior angles is for any polygon, and shows how to find the measure of individual exterior angles for regular polygons with a drawn example.
Texas Education Agency
Texas Gateway: Making Conjectures About Other Polygons
Given information about the properties of polygons, students will verify theorems about the relationships, including the sum of interior angles, and apply these relationships to solve problems.
Math Is Fun
Math Is Fun: Triangles Contain 180 Degrees
Students learn about the angle-sum theorem. A definition, example, and proof are included.
Sophia Learning
Sophia: Using Triangles to Find the Sum of Interior Angles: Lesson 1
This lesson demonstrates how to use triangles to determine the sum of the interior angles of a polygon. It is 1 of 5 in the series titled "Using Triangles to Find the Sum of Interior Angles."
Sophia Learning
Sophia: Triangle Interior Angles Practice: Lesson 5
This lesson provides practice problems that involve the sum of the interior angles of triangles. It is 5 of 6 in the series titled "Triangle Interior Angles Practice."
Sophia Learning
Sophia: Triangle Interior Angles Practice: Lesson 1
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."
Windstream
Ojk's Precalculus Study Page: Double and Half Angle Formulas
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.
University of Colorado
University of Colorado: Ph Et Interactive Simulations: Vector Addition
Learn how to add vectors. Drag vectors onto a graph, change their length and angle, and sum them together. The magnitude, angle, and components of each vector can be displayed in several formats.
University of Colorado
University of Colorado: Ph Et Interactive Simulations: Vector Addition
Learn how to add vectors. Drag vectors onto a graph, change their length and angle, and sum them together. The magnitude, angle, and components of each vector can be displayed in several formats.
Calculator Soup
Calculator Soup: Triangle Theorems Calculator
Each calculation option has sub-bullets that list the sequence of methods used in this calculator to solve for unknown angle and side values including Sum of Angles in a Triangle, Law of Sines, and Law of Cosines.
Cuemath
Cuemath: Obtuse Triangle
In this mini-lesson, learn about obtuse triangles including the obtuse triangle definition, sides, properties, examples, and other fun facts related to it.
Cuemath
Cuemath: Triangles
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.
National Council of Teachers of Mathematics
The Math Forum: Problems Library Geometry Triangles
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...
Texas Instruments
Texas Instruments: Properties of the Centers of a Triangle
Students investigate the sum of the measures of the interior angles of a triangle. This activity explores interior angles, and their relationship with the exterior angles of a triangle [Requires Adobe Reader.]
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