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- Problem Statement
- An acute ##\triangle ABC##, inscribed in a circle ##k## with radii ##R##, is given. Point ##H## is the orthocenter of ##\triangle ABC## and ##AH=R##. Find ##\angle BAC##. (Answer: ##60^\circ##)

- Relevant Equations
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##AD## is diameter, thus ##\angle ACD = \angle ABD = 90^\circ##. Also ##HBDC## is a parallelogram because ##HC||BD, HB||CD##. It seems useless and I don't know how to continue. Thank you in advance!