The LaTeX command for bra is \langle \psi | (Dirac bra (quantum mechanics)).
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Write \langle \psi | inside math mode, that is between $…$ for inline math or in a \[ … \] or equation block for display math. It is part of core LaTeX math, so no extra package is required.
The physics and siunitx packages offer shortcuts for many formulas, but \langle \psi | works in plain LaTeX.
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\nabla\nabla^2\nabla \cdot\nabla \times\partial\dot{x}\ddot{x}| \psi \rangle\langle \phi | \psi \rangle\rightleftharpoons\text{\AA}^\circ\mathrm{C}\infty\daggerPhysics symbols in LaTeX: the full table or search all 350+ LaTeX symbols.
Use \langle \psi | in math mode; it needs no extra package. For example, $\langle \psi |$.
None: \langle \psi | is built into LaTeX, so no extra package is required.