Let $Q$ be a smooth $n$-manifold, let $N\subset Q$ be an embedded $k$-dimensional submanifold, and let $\pi:T^*Q\to Q$ be the cotangent bundle projection. Define the conormal bundle of $N$ in $Q$ by
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\begin{align*}
T_N^*Q:=\{\alpha\in T^*Q:\pi(\alpha)\in N\text{ and }\alpha(v)=0\text{ for every }v\in T_{\pi(\alpha)}N\}.
\end{align*}
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Then $T_N^*Q$ is a Lagrangian submanifold of $(T^*Q,\omega_{\mathrm{can}})$, where $\omega_{\mathrm{can}}=-d\lambda$ and $\lambda$ is the tautological one-form on $T^*Q$.