Isosceles Triangle ABC: Calculate and Classify the 45° Vertex Angle

Question

Triangle ABC isosceles.

AB = BC

Calculate angle ABC and indicate its type.

00:00 Find angle ABC

00:04 The triangle is isosceles according to the given information

00:12 In an isosceles triangle, the base angles are equal

00:29 The sum of angles in a triangle equals 180

00:32 Therefore, we subtract the known angles from 180 to find ABC

00:41 This is angle ABC, an angle equal to 90 is a right angle

00:46 And this is the solution to the problem

Given that it is an isosceles triangle: $AB=BC$

It is possible to argue that: $BAC=ACB=45$

Since the sum of the angles of a triangle is 180, the angle ABC will be equal to:

$180-45-45=90$

Since the angle ABC measures 90 degrees, it is a right triangle.

90°, right angle.