Working on the book: Lange, Serge. "Basic Mathematics" (p. 119, exercise 1).
Finding the area of the sector determined by the angle in exercise a (area of disc is $60in^2)$:
Let $S$ be the sector determined by $A$ in the disc $D$ centered at $P$. Let $A_S$ and $A_D$ denote area of sector $S$ and disc $D$, respectively. I proceed to calculate the area of sector S:
$ \begin{align*} \frac{A_S}{A_D}&=\frac{60°}{360°}\\ A_S&=\frac{60°\cdot60in^2}{360°}=10in^2 \end{align*} $
The author solution is $1in^2$.
What's the correct answer ?