  The measurement of $\sin {2\beta}$ from $B_d \to J/\psi K_s$ does not resolve
the discrete ambiguities in the angle $\beta$. A measurement of $\cos {2\beta}$
is therefore desirable.This talk is about measuring the CKM angle
$\beta(\phi_1)$ from various B decays to charm final states which also allow us
a measurement of $\cos {2\beta}$.
