# Errata

## Chapter 4

On page 97, in the section "Factorizing and Expanding Expressions", the
expand function should be imported before we can use it via
`from sympy import expand`.

On page 99, in the code snippet on Line (2) and the following, the indentation is wrong. It should be:

for i in range(2, n+1): series = series + (x**i)/i

(Thanks to Taylan Yemliha)

On page 112, an import is missing - SympifyError used later in the try..except block. The initial import statement should hence be:

from sympy import Symbol, sympify, solve, SympifyError

(Thanks to Robert Buckley for pointing it out)

## Chapter 5

On page 132, in the section "Probability", the program should start
with the import statment `from sympy import FiniteSet`. (Thanks to
Dexter Edge)

On page 132, in the section "Probability," the code line above the one
marked with a (3), which reads `for num in s:` should instead read:
`for num in space`.

On page 139, in the code for simulating a fictional ATM, the statement
`probability = [1/6, 1/6, 1/3, 2/3]` should be `probability = [1/6,
1/6, 1/3, 1/3]`. (Thanks to Luis Soares)

## Chapter 6

On page 164 and 165, the transformation equations have some errors in the text (not in the program). The equations should be:

**Transformation 1**

x1 = 0.85*x + 0.04*y

y1 = -0.04*x + 0.85*y + 1.6

**Transformation 2**

x1 = 0.2*x - 0.26*y

y1 = 0.23*x + 0.22*y + 1.6

**Transformation 3**

x1 = -0.15*x + 0.28*y

y1 = 0.26*x + 0.24*y + 0.44

**Transformation 4**

x1 = 0

y1 = 0.16*y

(Thanks to Dexter Edge, Fatih Kürşat Cansu, Toshiaki Kurokawa and Twitter @mkamimura)

## Chapter 7

On page 195, an import is missing - SympifyError used later in the try..except block. The initial import statement should hence be:

from sympy import Derivative, Symbol, sympify, SympifyError

(Thanks to Robert Buckley for pointing it out)