Ceiling Function/Examples/Ceiling of -1.1

Theorem

 * $\ceiling {-1 \cdotp 1} = -1$

where $\ceiling x$ denotes the ceiling of $x$.

Proof
We have that:
 * $-2 < -1 \cdotp 1 \le -1$

Hence $-1$ is the ceiling of $-1 \cdotp 1$ by definition.

Also see

 * Floor of $1 \cdotp 1$: $\floor {1 \cdotp 1} = 1$
 * Floor of $-1 \cdotp 1$: $\floor {-1 \cdotp 1} = -2$