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Mar 8, 2023 at 13:29 comment added Jeremy Rickard @R.vanDobbendeBruyn I don’t know a reference, sorry. The way I saw this was not by writing down explicit homotopies, but by the fact that the obvious map from $\rho^{>0}A^\bullet$ to the mapping cone is split monic in each degree, and its cokernel is contractible (being the cone of the identity map on $\cdots\to A^{-2}\to A^{-1}\to 0\to\cdots$. I’m sure you can figure out explicit homotopies from that.
Mar 8, 2023 at 12:26 comment added R. van Dobben de Bruyn Do you have a reference for the homotopy equivalence $\operatorname{Cone}(\tau^{\leq 0}A^\bullet \to A^\bullet) \simeq \rho^{>0}A^\bullet$? I tried doing something like this, but couldn't find the correct homotopy...
Mar 8, 2023 at 10:03 vote accept CommunityBot
Mar 8, 2023 at 9:47 history edited Jeremy Rickard CC BY-SA 4.0
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Mar 8, 2023 at 8:58 history edited Jeremy Rickard CC BY-SA 4.0
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Mar 8, 2023 at 8:44 history answered Jeremy Rickard CC BY-SA 4.0