On products of beta and gamma elements in the homotpy of the first Smith-Toda spectrum

In this paper, we determine the first cohomology of the monochromatic comodule $M_2^1$ at an odd prime, and apply the results to show non-trivialities of some products of beta and gamma elements in the homotopy groups of the Smith-Toda spectrum $V(1)$. The cohomology for a prime greater than three was determined by the first author. Here, we verify them and determine the cohomology at the prime 3 by elementary calculation. The cohomology will be a stepping stone for computing the cohomology of the monochromatic comodule $M_0^3$, which we hope to determine for a long time.