In: Math
The Couchy product of two absolutely convergent series converges absolutely.
Let be two absolutely convergent series. Then the sequence
Suppose
then,
and being monotone sequence that is increasing and bounded by above must converge.
Define,
Then Converges absolutely. we have,
and
This shows and since converges,
must also converge absolutely.
Hence, The Couchy product of two absolutely convergent series converges absolutely.
Let be two absolutely convergent series. Then the sequence