Let $B$ be a standard brownian motion and $$ X_t=\int_0^t B_s \, ds. $$ What is the quadratic variation $[X]_t$ of $X$?
I see $dX_t$ as an sde with drift term $B_t$.
2026-02-23 20:42:27.1771879347
Quadratic variation of $X_t=\int_0^t B_s \, ds$
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$[X]=0$ since $X$ has finite variation.