What can we learn from B+→D(∗)−sK+π+, Bd→Ds(∗)−K0π+ and Bd→Ds(∗)−K∗+ decays?

We study the nonresonant three-body decays of B+→D(∗)−sK+π+ and Bd→Ds(∗)−K0π+. We find that these decays can provide the information on the time-like form factors of D(∗)sK. We also explicitly investigate Bd→Ds(∗)−K∗+ decays by discriminating the nonresonant contributions with the unknown D(∗)s wave functions being fixed by the measured mode of Bd→Ds−K+.