# Nabla cosine

Let $\mathbb{T}$ be a time scale and $p \in C_{ld}$ and $-\nu p^2 \in \mathcal{R}_{\nu}$.
$${\hat{\cos}_p(t,s)}=\dfrac{\hat{e}_{ip}(t,s)+\hat{e}_{-ip}(t,s)}{2}$$
## $\nabla$-special functions on time scales
$\nabla$-$\widehat{\cos}_p$$\nabla-\widehat{\cosh}_p$$\nabla$-$\widehat{e}_p$$\nabla-h_k$$\nabla$-$g_k$$\nabla-\widehat{\sin}_p$$\nabla$-$\widehat{\sinh}_p$