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Aug 15, 2024 at 17:01 vote accept Rusurano
Aug 10, 2024 at 12:23 answer added RobinSparrow timeline score: 2
Aug 10, 2024 at 8:53 comment added Feng $\angle DHH_1+\angle H_1HH_2=180^\circ$, and in quadrilateral $AH_1HH_2$ we have $\angle A+\angle AH_1H+\angle H_1HH_2+\angle AH_2H=360^\circ$, hence $\angle A+\angle H_1HH_2=180^\circ$. Therefore, $\angle DHH_1=\angle A$.
Aug 10, 2024 at 8:52 comment added peterwhy $\angle HDH_1 = 90^\circ -\angle A$, $\angle DHH_1 = 90^\circ -\angle HDH_1$.
Aug 10, 2024 at 8:46 history asked Rusurano CC BY-SA 4.0