A, B and C are points on the circumference of a circle. XY is a tangent to the circle at the point A.
Angle BAY = 72º and angle ABC = 54º.
Prove that triangle ABC is an isosceles
triangle.
You must give a reason for any statement
that you make or any calculation that you
carry out.

see explanation

Step-by-step explanation:

The angle between a tangent and a chord is equal to the angle in the alternate segment, then

∠ ACB = ∠ BAY = 72° , thus

∠ BAC = 180° - (72 + 54)° = 180° - 126° = 54°

Since ∠ BAC = ∠ ABC = 54°

Then Δ ABC is an isosceles triangle

its a straight line parallel to the time axis