# Book:David Nelson/The Penguin Dictionary of Mathematics/Second Edition/Errata

## Errata for 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.)

### Directed Angle

angle
Often an angle is regarded as the measure of the rotation involved in moving from one initial axis to another final axis (termed a direction angle).

### Eugenio Beltrami

Beltrami, Eugenio (1835-99)

### William Brouncker

Brouncker, William, Viscount (1620-85)

### Edward Cocker

Cocker, Edward (1631-75)

### Nikolai Ivanovich Lobachevsky

Lobachevsky, Nikolai Ivanovich (1793-1856)

### Pietro Mengoli

Mengoli, Pietro (1626-82)

### Emmy Noether

Noether, Amalie (Emmy) (1883-1935)

### William Oughtred

Oughtred, William (1575-1660)

### Rhombohedron

rhombohedron
A hexagonal prism.

### Willebrord van Royen Snell

Snell, Willebrord van Royen (1580-1626)

### Alfred Tarski

Tarski, Alfred (1902-85)

### Wronskian

Wronskian
It is named after the Polish mathematician Józef Maria Hoene-Wroński (1776-1853).

### Primitive of $\sqrt {x^2 - a^2}$

$\ds \int \sqrt {x^2 - a^2} \rd x = \frac 1 2 a^2 \cosh^{-1} \frac x a + \frac 1 2 {x \sqrt {x^2 - a^2} } + C$