Analyses of ${\mathit{D}}^{+}\to {\mathit{K}}_{\mathit{S}}^0{\mathit{K}}^{+}$ and ${\mathit{D}}^{+}\to {\mathit{K}}_{\mathit{S}}^0{\pi }^{+}$

Using data collected with the CLEO II detector at the Cornell Electron Storage Ring, we present new measurements of the branching fractions for $D^{+}\to K_S{K}^{+}$ and $D^{+}\to K_S{\pi }^{+}$. These results are combined with other CLEO measurements to extract the ratios of isospin amplitudes and phase shifts for $D\to \mathrm{KK}$ and $D\to K\pi$.