# If $G$ is an acyclic graph, then every subgraph of $G$ is acyclic. [closed]

If $$G$$ is an acyclic graph, then every subgraph of $$G$$ is acyclic.

Suggestions for this exercise.

• It's obvious, if you think about what it says. – saulspatz Apr 11 at 0:09
• Forget about graphs and cycles. Think for a moment. – bubba Apr 11 at 0:38

Suppose you had a cyclic sub-graph $$G'$$ of $$G$$. Then there would be some cycle in $$G'$$. This cycle would also be a cycle in $$G$$, contradicting the hypothesis that $$G$$ is acyclic.