Finding Angle ADC in an Isosceles Triangle with Given Median

Question

ABC is an isosceles triangle.

AD is the median.

What is the size of angle $∢\text{ADC}$ ?

00:00 Find the size of angle ADC

00:03 AD is a median according to the given information, a median bisects the side

00:06 The triangle is isosceles according to the given information

00:10 In an isosceles triangle, the median is also the height

00:17 The height creates a right angle with the side it meets

00:23 And this is the solution to the question

In an isosceles triangle, the median to the base is also the height to the base.

That is, side AD forms a 90° angle with side BC.

That is, two right triangles are created.

Therefore, angle ADC is equal to 90 degrees.