Shodor Education Foundation
Triangle Area
While the instructional activity focuses on right triangles, this activity offers a great way to practice the area of all triangles through an interactive webpage. The activity begins with the class taking a square paper and cutting in...
EngageNY
Perimeter and Area of Triangles in the Cartesian Plane
Pupils figure out how to be resourceful when tasked with finding the area of a triangle knowing nothing but its endpoints. Beginning by exploring and decomposing a triangle, learners find the perimeter and area of a triangle. They...
Illustrative Mathematics
Area of a Trapezoid
Here is a straightforward example of how to apply the Pythagorean Theorem to find an unknown side-length of a trapezoid. Commentary gives additional information on proving that the inside of the trapezoid is a rectangle, but is...
EngageNY
An Area Formula for Triangles
Use a triangle area formula that works when the height is unknown. The eighth installment in a 16-part series on trigonometry revisits the trigonometric triangle area formula that previously was shown to work with the acute triangles....
Government of Hong Kong
Areas and Volumes - 2D Shapes
Unfortunately for young mathematicians, the world isn't made entirely of parallelograms, triangles, and trapezoids. After first learning the area formulas for these common shapes, students apply this new knowledge to...
Curated OER
Area of Tangram Pieces
Mathematicians calculate the area of a tangram piece without using formulas. They use a geometry journal to record activities during this lesson. They make a set of tangrams and use them to compute area. They use...
Curated OER
Finding the Area of an Equilateral Triangle
The problem seems simple: find the area of the equilateral triangle whose sides are each length 1. In fact, this same problem is solved in 8th grade, addressing a different Common Core standard, using the formula for area of a triangle...
EngageNY
Perimeter and Area of Polygonal Regions in the Cartesian Plane
How many sides does that polygon have? Building directly from lesson number eight in this series, learners now find the area and perimeter of any polygon on the coordinate plane. They decompose the polygons into triangles and use Green's...
Curated OER
Perimeter and Area 5
In this calculating area worksheet, middle schoolers use their problem solving skills and the information provided to find the area of 6 triangles.
EngageNY
Using Trigonometry to Determine Area
What do you do when you don't think you have enough information? You look for another way to do the problem! Pupils combine what they know about finding the area of a triangle and trigonometry to determine triangle area when they don't...
Alabama Learning Exchange
Triangle Area: No Height? Use the Sine
No height? No problem! Learners use their knowledge and a little help from GeoGebra to develop the Law of Sines formula. The Law of Sines helps to determine the height of triangles to calculate the area.
Curated OER
Area of a Triangle
Students solve the area of triangles. In this precalculus lesson, students are given two sides of a triangle and asked to calculate the area. They apply the law of sine and the side-angle-side area formula to solve.
Willow Tree
Surface Area of Three-Dimensional Figures
Lateral area and surface area are simple concepts, but calculating them is not as easy! Using formulas, learners calculate lateral area and surface area for the same three-dimensional figures. The resource discusses the formula variables...
Curated OER
Areas of Trapezoids, Rhombuses and Kites
Young scholars calculate the area of different polygons. In this geometry lesson, students find the area for trapezoids, rhombuses and kites.
Curated OER
Learning by Logic - Total Surface Area
Geometers calculate the area of plane surfaces using the formulas for the area of a square, rectangle, and triangle. They develop the formula for calculating the total surface area of two geometric solids: the cube and rectangular prism.
Curated OER
The Trapping of Trapezoids
This is a nice hands-on activity where young geometers create trapezoids and calculate their area by looking at areas of quadrilaterals and triangles.
EngageNY
The Scaling Principle for Area
As they investigate scaling figures and calculate the resulting areas, groups determine the area of similar figures. They continue to investigate the results when the vertical and horizontal scales are not equal.
EngageNY
Unknown Area Problems on the Coordinate Plane
Scholars determine distances on the coordinate plane to find areas. The instructional activity begins with a proof of the formula for the area of a parallelogram using the coordinate plane. Pupils use the coordinate plane to determine...
Curated OER
Two Triangles' Area
Need an activity for teaching the Pythagorean Theorem? Geometry juniors apply the Pythagorean theorem to two triangles to determine a final calculation.
Curated OER
Areas of Polygons
Young mathematicians calculate the area of polygons in this algebra lesson. They find the determinant as they calculate the areas for triangles and quadrilaterals. They also use scalar multiplication to find the determinant.
Texas Instruments
Identifying a Triangle by its Sides and Angles
Identify triangles by their angle measures and side lengths by looking at and measuring angle measures and side lengths. Use Cabri Jr. to construct various triangles, then manipulate the construction to create the 6 types of triangles,...
Curated OER
The Pythagorean Theorem and Classifying Triangles
Through the examination of the relationship between the lengths of the sides of a triangles students will learn the classification of triangles (acute, right, or obtuse).
EngageNY
Composite Area Problems
The 21st segment in a 28-part series provides learners with area problems involving composite figures. To find the solution, pupils must decide whether to add or subtract areas. The composite figures are composed of quadrilaterals,...
Curated OER
Principles of Square Roots Lesson Plan
Middle and high schoolers investigate all the different places in math that square root is present. In this geometry instructional activity, pupils discuss square roots as it relates to a right triangle and construction. They go over...