Math Problem Statement

In the figure, AB || EF. Find the value of b.

Solution

To solve the problem, we use the given information:

  1. AB is parallel to EF (ABEFAB \parallel EF): This implies that certain angle relationships arise due to parallel lines, such as corresponding angles and supplementary angles.

  2. The angles provided:

    • CAB=228\angle CAB = 228^\circ
    • EDF=293\angle EDF = 293^\circ
    • CEF=32\angle CEF = 32^\circ
    • We are solving for bb^\circ (angle DCE\angle DCE).

Step-by-Step Solution:

Step 1: Analyze supplementary angles on a straight line.

  • At point AA, the angle CAB=228\angle CAB = 228^\circ exceeds 180180^\circ, so it spans both the exterior and interior regions. This means the reflex part is: \text{Interior angle at A} = 228^\circ - 180^\circ = 48^\circ.

Step 2: Use parallel line properties and the transversal.

  • The interior angle at AA (4848^\circ) corresponds to the angle at EE on the opposite side of the transversal, due to alternate interior angles. So: CEF=48.\angle CEF = 48^\circ.

Step 3: Solve for bb^\circ using triangle angle sum.

  • In CDE\triangle CDE, the sum of angles is 180180^\circ. The known angles are:
    • CEF=32\angle CEF = 32^\circ (given),
    • CED=293180=113\angle CED = 293^\circ - 180^\circ = 113^\circ (interior part of the reflex angle at DD).
  • Using the triangle angle sum property: b+32+113=180.b^\circ + 32^\circ + 113^\circ = 180^\circ.

Step 4: Simplify for bb.

b=18011332=35.b^\circ = 180^\circ - 113^\circ - 32^\circ = 35^\circ.

Final Answer:

b=35b = 35^\circ

Let me know if you need further clarifications or assistance! Here are some follow-up questions to deepen understanding:

  1. What are the alternate interior angle and corresponding angle properties in parallel lines?
  2. Why is the triangle angle sum always 180180^\circ?
  3. Can you identify another angle in the diagram if one more is missing?
  4. How do reflex angles work in geometry?
  5. Why does ABEFAB \parallel EF lead to specific angle relationships?

Tip: When working with parallel lines, always look for transversals and use properties like corresponding and alternate interior angles!

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Math Problem Analysis

Mathematical Concepts

Angles formed by parallel lines and a transversal
Triangle angle sum property
Reflex angles

Formulas

Sum of angles in a triangle = 180°
Supplementary angles sum to 180°

Theorems

Alternate interior angle theorem
Triangle angle sum theorem

Suitable Grade Level

Grades 8-10