This short video and interactive assessment activity is designed to teach second graders an overview of quarter-circles and semi-circles.
This short video and interactive assessment activity is designed to give fourth graders an overview of quarter-circles and semi-circles.
This lesson unit is intended to help you assess how students reason about geometry and, in particular, how well they are able to: use facts about the angle sum and exterior angles of triangles to calculate missing angles; apply angle theorems to parallel lines cut by a transversal; interpret geometrical diagrams using mathematical properties to identify similarity of triangles.
This short video and interactive assessment activity is designed to teach third graders an overview of reflective symmetry.
This short video and interactive assessment activity is designed to teach first graders an overview of quarter-circles and semi-circles.
This short video and interactive assessment activity is designed to teach third graders about identifying the properties of squares.
Per April
Per April
In this effort from YouCubed at the Stanford Graduate School of Education, the Indigenous Mathematics Educators Group shares new teaching resources for Indigenous art that is beautifully mathematical. Having students notice and wonder about this art can help them learn about mathematics, art, and Indigenous cultures. Resources include Indigenous mathematical art and lessons with questions to guide mathematical discussions.
On a hike with her children, Mrs. Thompson noticed the reflection of the top of a pine tree in a puddle in the path. Her son, who is almost a foot taller than she is, could not see the top of the tree in the puddle until he moved. Why did her son need to move to see the top of the tree? How can they use similar right triangles and indirect measurements to find the height of the tree?
If two inscribed angles intercept the same arc, then the angles are equal. Drag the orange points to change the figure.
An interactive applet and associated web page that demonstrate the inscribed angle of a circle - the angle subtended at the periphery by two points on the circle. The applet presents a circle with three points on it that can be dragged. The inscribed angle is shown and demonstrates that it is constant as the vertex is dragged. Links to other related topics such as Thales Theorem. Applet can be enlarged to full screen size for use with a classroom projector. This resource is a component of the Math Open Reference Interactive Geometry textbook project at http://www.mathopenref.com.
This task shows how to inscribe a circle in a triangle using angle bisectors. A companion task, ``Inscribing a circle in a triangle II'' stresses the auxiliary remarkable fact that comes out of this task, namely that the three angle bisectors of triangle ABC all meet in the point O.
This task is primarily for instructive purposes but can be used for assessment as well. Parts (a) and (b) are good applications of geometric constructions using a compass and could be used for assessment purposes but the process is a bit long since there are six triangles which need to be constructed.
This task provides an opportunity for students to apply triangle congruence theorems in an explicit, interesting context.
This problem introduces the circumcenter of a triangle and shows how it can be used to inscribe the triangle in a circle. It also shows that there cannot be more than one circumcenter.
This task focuses on a remarkable fact which comes out of the construction of the inscribed circle in a triangle: the angle bisectors of the three angles of triangle ABC all meet in a point.
This lesson unit is intended to help teachers assess how well students are able to use geometric properties to solve problems. In particular, it will help you identify and help students who have difficulty: decomposing complex shapes into simpler ones in order to solve a problem; bringing together several geometric concepts to solve a problem; and finding the relationship between radii of inscribed and circumscribed circles of right triangles.
An interactive applet and associated web page that demonstrate the relationship of the interior and exterior angles of a polygon. The applet shows an irregular polygon where one vertex is draggable. As it is dragged the interior and exterior angles at that vertex are displayed, and a formula is continuously updated showing that they are supplementary. The tricky part is when the vertex is dragged inside the polygon making it concave. The applet shows how the relationship still holds provided you get the signs of the angles right. Applet can be enlarged to full screen size for use with a classroom projector. This resource is a component of the Math Open Reference Interactive Geometry textbook project at http://www.mathopenref.com.
The lesson starts with a review of basic geometric terms.Angles are defined.There are four types of angles.A right angle measures 90° and forms a square corner. If you were to sit inside a right angle, you would be sitting straight up.An acute angle measures less than 90° and is open less than a right angle. Acute angles have a smaller measurement. Think of them as small and cute. =) If you were sitting inside an acute angle, you would be bent together like a 'V'.An obtuse angle measures more than 90° and is open more than a right angle. Obtuse angles have a larger measurement. If you were to sit inside a obtuse angle, you would be leaning back as if you were lounging in a beach chair by the pool.A straight angle measures exactly 180° and forms a straight line. If you were to sit inside a straight angle, you would actually have to lay down flat on your back.