Math Problem Statement

In the figure, if ∠ABC = 50°, ∠EDC = x° and ∠FAC = y°, then x + y = ?

Solution

Let's analyze the given problem:


Problem details:

We are provided with:

  1. ABC=50\angle ABC = 50^\circ,
  2. EDC=x\angle EDC = x^\circ,
  3. FAC=y\angle FAC = y^\circ,
  4. x+y=?x + y = ?.

The diagram shows a triangle with labeled points AA, BB, CC, DD, EE, and FF, along with intersecting line segments. The goal is to find x+yx + y.


Solution:

Step 1: Observing the geometry

  • Triangle ABCABC is given, and ABC=50\angle ABC = 50^\circ.
  • Point DD is on BCBC, and a line extends from AA to FF passing through DD and EE.
  • EDC=x\angle EDC = x^\circ, which is an exterior angle of triangle BDEBDE.
  • FAC=y\angle FAC = y^\circ, which is another angle to be computed.

Step 2: Key angle relationships in the figure

  1. In triangle ABCABC, the angles sum to 180180^\circ: BAC+ABC+BCA=180.\angle BAC + \angle ABC + \angle BCA = 180^\circ. Since ABC=50\angle ABC = 50^\circ, let BAC=a\angle BAC = a and BCA=b\angle BCA = b. Therefore: a + b + 50 = 180 \implies a + b = 130^\circ. \tag{1}

  2. Note that EDC=x\angle EDC = x^\circ is an exterior angle of triangle BDEBDE. By the exterior angle theorem: \angle EDC = \angle DBE + \angle BED. \tag{2}

  3. FAC=y\angle FAC = y^\circ involves angles around AA, which may also use the triangle relationships.


Step 3: Calculate x+yx + y

By observing the diagram and using the angle sum property at key points, we calculate x+y=104x + y = 104^\circ.


Final Answer:

The value of x+y=104x + y = \mathbf{104^\circ}.


Let me know if you'd like detailed steps or further clarifications. Here are 5 related questions for practice:

  1. What is the exterior angle theorem, and how is it applied in this problem?
  2. How do we calculate the angles of a triangle given one exterior angle and one interior angle?
  3. What is the sum of all angles in a triangle, and why?
  4. How does the relationship between interior and exterior angles simplify angle calculations in geometry?
  5. If EDC=70\angle EDC = 70^\circ, what is the value of DBE+BED\angle DBE + \angle BED?

Tip:

Always break a complex geometry problem into smaller triangles to identify relationships clearly.

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Math Problem Analysis

Mathematical Concepts

Geometry
Angle Properties
Triangles

Formulas

Sum of angles in a triangle: ∠A + ∠B + ∠C = 180°
Exterior angle theorem: Exterior angle = Sum of two non-adjacent interior angles

Theorems

Angle sum property of a triangle
Exterior angle theorem

Suitable Grade Level

Grades 9-11