Book:Walter Ledermann/Complex Numbers/Errata

Argument of $-1 - i$
Chapter $2$: Geometrical Representations: Example $\text{(iv)}$

Equation relating Points of Parallelogram in Complex Plane
Chapter $2$: Geometrical Representations: Exercise $7$

Triple Angle Formula for Cosine: $2 \cos 3 \theta + 1$
Chapter $3$: Roots of Unity: Example $6$

Radius of Convergence of Power Series Expansion for Cosine Function
Chapter $4$: Elementary Functions of a Complex Variable: Section $4$: Power Series: Example $\text{(iii)}$