# Math Help - Poincare's Theorem

1. ## Poincare's Theorem

Let H1 & H2 be subgroups of G. How can it be shown that if H1 & H2 have finite index in G then so the intersection of H1 & H2.

2. Originally Posted by thomas_donald

Let H1 & H2 be subgroups of G. How can it be shown that if H1 & H2 have finite index in G then so the intersection of H1 & H2.
Hint (acually the solution!!): $(H_1 \cap H_2)g=H_1g \cap H_2g,$ for all $g \in G.$