.
#/_ACS=/_ABC=67^@# because they both face arc #AC# and are half the measure of that arc.
#/_BAC=90^@# because it is an inscribed angle facing the diameter of the circle.
#/_BCT=180^@-(90^@+67^@)=23^@#
#/_ABC=/_BTC+/_BCT# because #/_ABC# is the exterior angle of triangle #DeltaBTC#.
#67^@=/_BTC+23^@#
#/_BTC=67^@-23^@=44^@#