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# Browse by Grade & Topic: Triangles

## Find Gizmos organized by grade level and topic.

See How FREE Gizmos WorkArea of Triangles

Use a dynamic triangle to explore the area of a triangle. With the help of an animation, see that any triangle is always half of a parallelogram (with the same base and height). Likewise, a...

Lesson Info Launch GizmoSegment and Angle Bisectors

Explore the special properties of a point that lies on the perpendicular bisector of a segment, and of a point that lies on an angle bisector. Manipulate the point, the segment, and the...

Lesson Info Launch GizmoConcurrent Lines, Medians, and Altitudes

Explore the relationships between perpendicular bisectors, the circumscribed circle, angle bisectors, the inscribed circle, altitudes, and medians using a triangle that can be resized and...

Lesson Info Launch GizmoCongruence in Right Triangles

Apply constraints to two right triangles. Then drag their vertices around under those conditions. Determine under what conditions the triangles are guaranteed to be congruent.

Lesson Info Launch GizmoIsosceles and Equilateral Triangles

Investigate the graph of a triangle under constraints. Determine which constraints guarantee isosceles or equilateral triangles.

Lesson Info Launch GizmoProving Triangles Congruent

FREE *with no time limit!*

Apply constraints to two triangles. Then drag the vertices of the triangles around and determine which constraints guarantee congruence.

Lesson Info Launch GizmoSimilarity in Right Triangles

Divide a right triangle at the altitude to the hypotenuse to get two similar right triangles. Explore the relationship between the two triangles.

Lesson Info Launch GizmoTriangle Angle Sum

Measure the interior angles of a triangle and find the sum. Examine whether that sum is the same for all triangles. Also, discover how the measure of an exterior angle relates to the...

Lesson Info Launch GizmoTriangle Inequalities

Discover the inequalities related to the side lengths and angle measures of a triangle. Reshape and resize the triangle to confirm that these properties are true for all triangles.

Lesson Info Launch GizmoArea of Parallelograms

Examine and manipulate a parallelogram and find its area. Explore the relationship between the area of a parallelogram and the area of a rectangle using an animation.

Lesson Info Launch GizmoClassifying Triangles

Place constraints on a triangle and determine what classifications must apply to the triangle.

Lesson Info Launch GizmoProving Triangles Congruent

FREE *with no time limit!*

Apply constraints to two triangles. Then drag the vertices of the triangles around and determine which constraints guarantee congruence.

Lesson Info Launch GizmoHow Free Gizmos Work

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**20-40 Free Gizmos**. See the full list.

Access **lesson materials** for Free Gizmos including teacher guides, lesson plans, and more.

All other Gizmos are limited to a **5 Minute Preview** and can only be used for 5 minutes a day.

**Free Gizmos change each semester.** The new collection will be available Jul 01, 2023.

About STEM Cases

Students assume the role of a scientist trying to solve a real world problem. They use scientific practices to collect and analyze data, and form and test a hypothesis as they solve the problems.

Each STEM Case uses realtime reporting to show live student results.

Introduction to the Heatmap

STEM Cases take between 30-90 minutes for students to complete, depending on the case.

Student progress is automatically saved so that STEM Cases can be completed over multiple sessions.

Multiple grade-appropriate versions, or levels, exist for each STEM Case.

Each STEM Case level has an associated Handbook. These are interactive guides that focus on the science concepts underlying the case.

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