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$45^{\circ }$
$\angle AOC$
$\angle COD$
$\angle AOB$
$90'$ $30.5^{\circ }$
图中$\angle EOA$是反射角.
$\angle EOA \lt \angle EOB \lt \angle EOC \lt \angle EOD$
6个角,$\angle AOB$,$\angle AOC$,$\angle AOD$,$\angle BOC$,$\angle BOD$,$\angle COD$.
$\angle AOB=\angle AOC-\angle BOC=$$50^{\circ }-20^{\circ }15'=29^{\circ }45'$.
6个角,$\angle AOB$,$\angle AOC$,$\angle AOD$,$\angle BOC$,$\angle BOD$,$\angle COD$.