Question

Triangle ABC is an isosceles right triangle inscribed in a circle. The center of the circle is point D and the diameter of the circle is AC.
Which of the following would not be true for the triangle and circle described above?

See Attached for choices

Answer 1

Answer:

* AD is congruent to DC and BD true

* m∠B = 90° true

* The measure of arc AC is equal to the measure of arc AB not be true ( The right answer  )

* The measure of arc AB is equal to measure of arc BC true

Step-by-step explanation:

∵ D is the center of the circle and A , B and C are points on the circle

∴ AD , DB and DC are radii on the circle D

∴ AD ≡ DC ≡ DB

∵ AC passing through point D which is the center of the circle

∴ AC is the diameter of the circle D

∵ ∠B is opposite to the diameter of the circle and vertex B lies on the circle

∵ ∠B is an inscribed angle and  ∠ADC  is a central angle subtended by the same arc AC

∴m∠B = half m∠ADC

∵ m∠ADC = 180°

∴ m∠B = 90°

∵ The measure of arc AC = 180°

∵ ΔABC is isosceles and m∠B = 90°

∴ m∠BAC = m∠BCA = (180° - 90°) ÷ 2 = 45°

∵ ∠ACB is an inscribed angle subtended by arc AB

∴ m∠ACB = half measure of arc AB

∵ The measure of arc AB = 45° × 2 = 90°

∴ The measure of arc AC ≠ the measure of arc AB

∵ Δ ABC is an isosceles triangle and m∠B = 90°

∴ AB = BC

∵ AB subtended by arc AB

∵ BC subtended by arc BC

∴ The length of arc AB = the length of arc BC

∵ If two arcs are equal in length, then they will be equal in measure

∴ The measure of arc AB is equal to the measure of arc BC