In this exercise, students identify and draw slices through an ice cream cone, a pyramid, and a beverage six-pack.

The purpose of this task is to lead students through an algebraic approach to a well-known result from classical geometry, namely, that a point X is on the circle of diameter AB whenever _AXB is a right angle.

Total solar eclipses are quite rare, so much so that they make the news when they do occur. This task explores some of the reasons why. Solving the problem is a good application of similar triangles

This short video and interactive assessment activity is designed to teach third graders about identifying and naming 3d figures.

This short video and interactive assessment activity is designed to teach second graders about identifying and naming 3d figures.

This short video and interactive assessment activity is designed to give fifth graders an overview of squares and rectangles.

This task presents a foundational result in geometry, presented with deliberately sparse guidance in order to allow a wide variety of approaches. Teachers should of course feel free to provide additional scaffolding to encourage solutions or thinking in one particular direction. We include three solutions which fall into two general approaches, one based on reference to previously-derived results (e.g., the Pythagorean Theorem), and another conducted in terms of the geometry of rigid transformations.

The construction of the tangent line to a circle from a point outside of the circle requires knowledge of a couple of facts about circles and triangles. First, students must know, for part (a), that a triangle inscribed in a circle with one side a diameter is a right triangle. This material is presented in the tasks ''Right triangles inscribed in circles I.'' For part (b) students must know that the tangent line to a circle at a point is characterized by meeting the radius of the circle at that point in a right angle: more about this can be found in ''Tangent lines and the radius of a circle.''

This short video and interactive assessment activity is designed to teach third graders an overview of tessellations.

 Objective:  Students will create their own tesselations and research and formulate opinions on M.C Escher.Activity Type/Purpose:  Individual creations by students along with guided questions to facilitate connecting art and mathematicsAudience:  Geometry Classroom 

This short video and interactive assessment activity is designed to give fifth graders an overview of tessellations.

This short video and interactive assessment activity is designed to give fourth graders an overview of tessellations.

This short video and interactive assessment activity is designed to teach fourth graders about determining unknown angles in composite figures.

This short video and interactive assessment activity is designed to teach third graders about determining unknown angles in composite figures.

Students extend their understanding of circles, volume, and surface area into modeling situations, formula analysis, and deeper conceptual understandings.

This 10-minute video lesson shows that three points uniquely define a circle and that the center of a circle is the circumcenter for any triangle that the circle is circumscribed about.

Khan Academy learning modules include a Community space where users can ask questions and seek help from community members. Educators should consult with their Technology administrators to determine the use of Khan Academy learning modules in their classroom. Please review materials from external sites before sharing with students.

ile patterns will be familiar with students both from working with geometry tiles and from the many tiles they encounter in the world. Here one of the most important examples of a tiling, with regular hexagons, is studied in detail. This provides students an opportunity to use what they know about the sum of the angles in a triangle and also the sum of angles which make a line.

This task aims at explaining why four regular octagons can be placed around a central square, applying student knowledge of triangles and sums of angles in both triangles and more general polygons.

The purpose of this task is to engage students in geometric modeling, and in particular to deduce algebraic relationships between variables stemming from geometric constraints. The modelling process is a challenging one, and will likely elicit a variety of attempts from the students.

This short video and interactive assessment activity is designed to teach third graders an overview: sum of the angles of a triangle.