Math Problem Statement

What is the value of x in the figure shown, where two isosceles triangles share a vertex angle at A, with AE = AC = 4.1, AD = AB = 2.9, angle A = 92°, and angle ACB = 35°?

Solution

We are tasked with finding the value of angle xx in the given figure. Let's analyze the geometry of the figure step by step.

  1. Given Information:

    • Triangle AECAEC has the side lengths AE=4.1AE = 4.1, AC=4.1AC = 4.1, and angle ACB=35\angle ACB = 35^\circ.
    • Triangle ADBADB has the side lengths AD=2.9AD = 2.9, AB=2.9AB = 2.9, and angle DAB=92\angle DAB = 92^\circ.
    • We are asked to find xx, which is the angle EAD\angle EAD.
  2. Observation:

    • Triangles AECAEC and ADBADB share the angle A\angle A, which is 9292^\circ.
    • Triangles AECAEC and ADBADB are isosceles, as two of their sides are equal (i.e., AE=AC=4.1AE = AC = 4.1 in triangle AECAEC and AD=AB=2.9AD = AB = 2.9 in triangle ADBADB).
  3. Step-by-Step Solution:

    • In triangle AECAEC, the sum of interior angles must be 180180^\circ. Therefore, the third angle AEC\angle AEC can be calculated as: AEC=180AACB=1809235=53.\angle AEC = 180^\circ - \angle A - \angle ACB = 180^\circ - 92^\circ - 35^\circ = 53^\circ.
    • Since triangle AECAEC is isosceles, the base angles EAC\angle EAC and AEC\angle AEC must be equal. Therefore, EAC=AEC=53\angle EAC = \angle AEC = 53^\circ.
    • In triangle AEDAED, we can now calculate the unknown angle xx (which is EAD\angle EAD) by using the fact that the angles in a triangle sum to 180180^\circ. We have: x+EAC+92=180.x + \angle EAC + 92^\circ = 180^\circ. Substituting EAC=53\angle EAC = 53^\circ: x+53+92=180,x + 53^\circ + 92^\circ = 180^\circ, x=180145=35.x = 180^\circ - 145^\circ = 35^\circ.

Thus, the value of xx is 3535^\circ.

Let me know if you'd like more details or further clarifications. Here are five related questions to explore:

  1. What are the properties of an isosceles triangle?
  2. How do you calculate the third angle in a triangle if two angles are known?
  3. What is the sum of angles in any triangle?
  4. How would the solution change if one of the triangles were not isosceles?
  5. Can you solve for unknown side lengths in this type of triangle using the Law of Cosines?

Tip: Always check if the triangle is isosceles when two sides are equal to simplify angle calculations.

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Math Problem Analysis

Mathematical Concepts

Isosceles Triangles
Angle Sum in a Triangle
Geometry

Formulas

Sum of angles in a triangle = 180°

Theorems

Isosceles Triangle Theorem

Suitable Grade Level

Grades 9-11