What is 54.3 - 19.74 using mental math
2 answers:
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Answer:
Step-by-step explanation:
see the attached figure to better understand the problem
step 1
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
----> 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 180 degrees
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 equal to 60 degrees
so
step 3
Find the measure of the angle ∠ABC
we know that
---> by addition angle postulate
substitute the values
