Illustrative Mathematics
Illustrative Mathematics: 6.g Same Base and Height, Variation 2
This is the second version of a task asking students to find the areas of triangles that have the same base and height. This presentation is more abstract as students are not using physical models. They still determine the area of each...
Math Is Fun
Math Is Fun: Heron's Formula
Learn a formula, created thousands of years ago, that you can use to calculate the area of a triangle if you know all three sides' lengths.
Texas Instruments
Texas Instruments: Surround and Be Found! Triangular Areas, That Is!
In this activity, students use the Geoboard to determine the area of triangles using the surrounding rectangle technique. They also develop and use formulas to determine the area of triangles. [Requires Adobe Reader.]
CK-12 Foundation
Ck 12: Trigonometry: Heron's Formula
[Free Registration/Login may be required to access all resource tools.] This lesson covers Heron's Formula and problem solving using trigonometry.
Texas Instruments
Texas Instruments: Investigating Properties of Trapezoids
Students draw trapezoids and investigate their properties. They derive the area formula for a triangle from the area formula for a trapezoid. They also investigate the terms: Isosceles trapezoid and Tessellation. Numerous supplementary...
Texas Instruments
Texas Instruments: Calculating the Area of a Triangle Using Heron's Formula
Students will measure the lengths of the sides of three different triangles and apply Heron's Formula to calculate the area in acres. The measurements for this activity may be done outside or, using a specified scale, completed inside....
Math Open Reference
Math Open Reference: Heron's Formula
Learn about corresponding angles with this resource which offers detailed explanations, examples, and interactives. Subjests covered include the area of a triangle. Links to related topics.
The Math League
The Math League: Area and Perimeter
This tutorial provides a brief introduction about what area is, then gives the formulas for area of a square, rectangle, parallelogram, trapezoid, triangle, and circle. Examples of each formula are provided.
CK-12 Foundation
Ck 12: Trigonometry: Alternate Formula for the Area of a Triangle
[Free Registration/Login may be required to access all resource tools.] An alternate formula for the area of a triangle.
Better Lesson
Better Lesson: Finding the Area of a Trapezoid
Sixth graders find the area of a trapezoid by decomposing it into triangles and using the formula
Illustrative Mathematics
Illustrative Mathematics: G C Mutually Tangent Circles
Three circles are mutually tangent. Students are asked to find the total area of the circles plus the area inside where they meet. Students will need to know how to calculate the area of a circle, a sector of a circle, and an equilateral...
Mocomi & Anibrain Digital Technologies
Mocomi: What Is Heron's Formula?
Define's Heron's Formula and provides examples for how to use the formula to calculate the area of a triangle.
Shmoop University
Shmoop: Basic Geometry: Area (Polygon, Triangle, Circle, Square)
The geometry resource investigates the area of polygons, triangles, circles, and squares. Formulas and examples are included.
Vernet -Virtual Education Resources Network
Salon Hogar: Referencia Rapida De Formulas Geometricas
This site provides the user with a useful reference to different geometric forms, their elements, formulas, and areas. Entirely in Spanish.
Texas Instruments
Texas Instruments: Heron's Formula
This activity allows students to find the area of a triangle using Heron's formula.
Wolfram Research
Wolfram Math World: Midpoint
This MathWorld site offers a lesson on finding the midpoint of a line segment using a compass and finding the midpoint of the sides of a triangle. This site also has an interesting way of drawing two triangle with equal area by finding...
OER Commons
Oer Commons: Polygons
Seventh graders find the area of regular polygons, recalling what they already know about the area of geometric shapes and generalizing a formula for any regular polygon.