Question 935736

recall: Thales' theorem states that if {{{A}}}, {{{B}}} and {{{C}}} are points on a circle where the line {{{AC}}} is a {{{diameter}}} of the circle, then the angle < {{{ABC}}} is a {{{right}}} angle.

then triangle {{{ABC}}} is  a {{{right}}} angle triangle

since the sum of all angles in a triangle {{{ABC}}} is {{{180}}}, then {{{x+y=90}}} =>that proves {{{ x=90-y}}}