# Modernization of Numerical Integration, From Quad to Integral

Posted by Cleve Moler,

The MATLAB functions for the numerical evaluation of integrals has evolved from quad, through quadl and quadgk, to today's integral. ... read more >>

# The Classic Crossed Ladders Puzzle

Posted by Cleve Moler,

Here is a classic puzzle. A pair of ladders leaning against the sides of an alley form a lopsided cross. Each ladder is propped against the base of one wall and leans against the opposite wall. If one ladder is 30 feet long, the other 20 feet long, and the point where they cross 10 feet above the ground, how wide is the alley?... read more >>

# Surprising SVD, Square Waves, and Pi2

Posted by Cleve Moler,

I am surprised when many of the singular values of a nonsymmetric variant of the Hilbert matrix turn out to be nearly equal to $\pi$. The explanation involves the Fourier series for a square wave.... read more >>