# 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.

$\blacksquare$