I have a question posted by my lecturer, but so far no one have been able to solve it yet
Let $\Bbb R$ be the set of real numbers.
The sets $C$ and $D$ are defined as follows:
$C = \{(a,b) \mid a^2 + b^2< 1,(a,b) ∈ \Bbb R\times \Bbb R\}$
$D = \{(a,b) \mid 2ab < 1,(a,b) ∈\Bbb R\times \Bbb R\}$
Prove or disprove $C$ is a subset of $D$.