# Search Results for “sometimes-quadrilateral”

##### Cyclic Quadrilateral Theorem

The Cyclic Quadrilateral Theorem states that for a quadrilateral inscribed in a circle, the measures of opposite angles must add to 180 degrees. Drag the points and observe the angle measures to see how this theorem holds true.##### Euclids Elements - Book 2 - Proposition 14

One of my favorite apps because it looks deceptively simple, but takes some really creative thinking. This app creates a square (in red) that has the same area as a given quadrilateral.##### Curve Area

E is the midpoint of AD and F is the midpoint of BC. A closed curve is made by joining the cubic spline whose control polygon is EABF to the spline whose control polygon is FCDE. Can you identify a relationship between the area of the curve and the area of the polygon ABCD?##### Epic Circle Trace 3

Four points are located proportionally around a circle, according to four different functions of*t*. A figure connecting the four points is traced through

*t*. What are the four functions? Look at the .gx source for the answer.

**Tip**: press "go" to animate

*t*at a constant rate from 0 to ∏ and back, looped.