Microworld: Marden's Theorem : (All in One)
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Author: Dan Kalman

Marden's theorem concerns polynomials over the complex numbers.

As a specific case, consider the polynomial p(z) = (z-a)(z-b)(z-c), where a, b, and c are fixed complex numbers, and z is a complex variable. We know that p has roots at a, b, and c, which we visualize as three points in the complex plane. If those points are not colinear, they define a triangle within which it is possible to inscribe an ellipse, tangent to the sides at their midpoints.

Marden's theorem says that the foci of the ellipse are precisely the roots of the derivative, p'(z).

In this Microworld, you may experiment with this, and a more general version of Marden's Theorem. And you may review properties of complex numbers and the complex plane, both visually and algebraically. This Microworld will also give you the opportunity to explore the geometry of ellipses inscribed in triangles. This is a "hands on" opportunity to investigate some beautiful correlations between algebra and geometry. At every step, the book invites you to ask questions, and to see for yourself what the answers to those questions are. You will enjoy this one!

Topics:complex numbers, complex arithmetic, cubic polynomials, geometry

Suggested Use: Experiment with the geometry of cubic polynomial equations.

Number of Pages: 10

Animation:Yes

Grade Level: Intermediate - Advanced College

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Microworld Title Page:
Marden's Theorem

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