In this article, an attempt is made to find all linear transformations that map a standard Pythagorean triple (a Pythagorean triple [x y z][superscript T] with y being even) into a standard Pythagorean triple, which have [3 4 5][superscript T] as their fixed point. All such transformations form a monoid S* under matrix product. It is found that S*…

Many students view equations as a series of variables and operators into which numbers should be plugged rather than as representative of a physical process. To solve a problem they may simply look for an equation with the correct variables and assume it meets their needs, rather than selecting an equation that represents the appropriate physical…

This article contains investigative activities to assist students in constructing formulas out of an understanding of the area of geometric shapes. Included with this article are a "Finding Areas on Square Dot Paper Activity Sheet" and a "Finding Areas on Triangle Dot Paper Activity Sheet." (Contains 1 table and 11 figures.)

A general and rigorous method to deal with singularities at the origin of a polar coordinate system is presented. Its power derives from a clear distinction between the radial distance and the radial coordinate variable, which makes that all delta functions and their derivatives are automatically generated, and ensures that the Gauss theorem is…

We illustrate the derivations of Jeans' criteria for the gravitational instabilities in a static homogeneous Newtonian system for pedagogical objectives. The critical Jeans density surface is presented in terms of dimensionless sound speeds and (characteristic) length scales. (Contains 1 figure.)

In this work, we present a simple analysis of binary diffraction gratings with different slit widths relative to the grating period. The analysis is based on a simple phasor technique directly derived from the Huygens principle. By introducing a slit phasor and a grating phasor, the intensity of the diffracted orders and the grating's resolving…

In this paper, the author investigates the algebraic curve defined by the relation y[superscript 3] - 3y + 2x = 0. Treating this relation as a reduced cubic in the variable y, he uses a procedure first discovered by the mathematician Scipione del Ferro (Nahin, 1998, pp. 8-10) to obtain an expression for y in terms of x, namely y = (-x + [square…

A common mistake in analysis of cluster randomized trials is to ignore the effect of clustering and analyze the data as if each treatment group were a simple random sample. This typically leads to an overstatement of the precision of results and anticonservative conclusions about precision and statistical significance of treatment effects. This…

Hill ciphers are linear codes that use as input a "plaintext" vector [p-right arrow above] of size n, which is encrypted with an invertible n x n matrix E to produce a "ciphertext" vector [c-right arrow above] = E [middle dot] [p-right arrow above]. Informally, a near-field is a triple [left angle bracket]N; +, *[right angle bracket] that…

The author of this paper submits the thesis that learning requires doing; only through inquiry is learning achieved, and hence this paper proposes a programme of use of a modified Moore method in a Probability and Mathematical Statistics (PAMS) course sequence to teach students PAMS. Furthermore, the author of this paper opines that set theory…

Understanding the way farmers respond to risk is a prerequisite for sound agricultural policymaking. Clarifying established agricultural economic theory to describe how individuals make choices among risky alternatives and providing a more precise set of concepts for studying behavior under risk contributes to such an understanding. A…

The proposed coefficient is derived by assuming that the average Goodman-Kruskal gamma between items of identical difficulty would be the same for items of different difficulty. An estimate of covariance between items of identical difficulty leads to an estimate of the correlation between two tests with identical distributions of difficulty.…

Recent work (EJ 208 813) showing that generalized eigenvalue problems in which both matrices are singular can be solved by reducing them to similar problems of smaller order is discussed. Possible extensions of the work are indicated. (Author/JKS)

The Relative Difficulty Ratio (RDR) was developed as an index of test or item difficulty for use when raw score means or item p-values are not directly comparable because of chance score differences. Computational RDR are described. Applications of the RDR at both the test and item level are illustrated. (Author/BW)

Examples are given to show how the semistrandardized (SS) regression coefficient provides information not given by the conventional standardized regression coefficients used in factor, canonical, and path analysis. (Author/RL)