Answer:
Step-by-step explanation:
Find the measure of the vertex angle ∠ABD of an isosceles triangle
we know that
An isosceles triangle has two equal sides and two equal angles
In this problem
∠ABD=∠BAD= ----> the angles of the base are equals
Find the measure of the vertex angle
∠ABD= ------> the sum of the internal angles of a triangle is equal to
Step 2
Find the measure of the angle ∠CBD in the equilateral triangle
we know that
A equilateral triangle has three equal sides and three equal angles
The measure of the internal angle in a equilateral triangle is
so
∠CBD=
Step 3
Find the measure of the angle ∠ABC
∠ABC=∠ABD+∠DBC
substitute the values
∠ABC=
therefore
the answer is
the measure of the angle ∠ABC is
