We use the $C_2$-equivariant Adams spectral sequence to compute part of the $C_2$-equivariant stable homotopy groups $\pi^{C_2}_{n,n}$. This allows us to recover results of Bredon and Landweber on the image of the geometric fixed-points map from the equivariant homotopy group $\pi^{C_2}_{n,n}$ to the classical $\pi_0$. We also recover results of Mahowald and Ravenel on the Mahowald root invariants of the elements $2^k$.