Scott Farrar
Back to Talks

California Mathematics Council North Conference at Asilomar

If a picture is worth 1000 words, what is GeoGebra worth?

A collection of dynamic mathematics demonstrations built around the claim that interaction can communicate more than a static diagram.

Scott Farrar · · Pacific Grove, California

Slides Handout Original archived page
A Euclidean geometry construction with a semicircle, intersecting lines, and labeled angles.

Context

A compact conference resource page with a handout, slides, HTML applets, and GeoGebra source files.

The original Word-generated HTML remains available for historical reference. This page is the main entry point.

The talk moved across geometry, algebra, trigonometry, and calculus. Its common thread was not a particular topic but a way of using dynamic diagrams: give learners something they can move, then let the mathematical structure answer back.

The applets are presented together because they were originally assembled as one conference argument rather than as nine unrelated files.

Interactive materials

Applets from the talk

GeoGebra scatterplot comparing rectangle area and perimeter values.

Area vs. Perimeter

Investigate which area and perimeter combinations are possible for rectangles, adapted from a Malcolm Swan prompt.

Open applet
GeoGebra unit circle diagram with trigonometric segment labels.

Unit Circle Trigonometry

Connect a rotating point on the unit circle to trigonometric values and their geometry.

Open applet
GeoGebra diagram connecting circular motion to a trigonometric graph.

Generating Sine and Cosine from the Circle

Use circular motion as a live generator for sine and cosine waves.

Open applet
GeoGebra diagram for Euclid's visual proof of the Pythagorean theorem.

Euclid's Pythagorean Proof

Step through a visual proof of the Pythagorean theorem and the geometric moves behind the result.

Open applet
GeoGebra epsilon-delta limit diagram with highlighted intervals.

Epsilon and Delta Limits

Manipulate epsilon and delta intervals so the formal limit definition has a dynamic picture.

Open applet
GeoGebra triangle inequality applet with a draggable third point.

Triangle Inequality Drag

Drag segment lengths and watch possible triangles appear, disappear, or collapse at the boundary.

Open applet
GeoGebra graph with curves controlled by visible linear factors.

Painting with Linear Factors

Use factors as visible controls for shaping a graph, adapted from Riley Lark's activity idea.

Open applet
GeoGebra applet showing quadrilaterals that may or may not remain squares when dragged.

Square Not Square

Compare what stays square, what only looks square, and what changes under dragging.

Open applet
GeoGebra applet plotting distances from a point to triangle vertices.

Distances to Vertices

Explore how distances from a movable point to triangle vertices change and what patterns emerge.

Open applet

Related writing

Ideas around the presentation