Math Problem Statement

3 lines are shown. A line with points A, F, D intersects a line with points B, F, E at point F. A line extends from point F to point C in between angle D F B. Angle A F E is 125 degrees and angle B F C is 45 degrees. What is mAngleDFC?

45° 80° 125° 135°

Solution

To solve for the measure of angle DFC\angle DFC, we need to carefully analyze the geometry based on the given information.

Steps to solve:

  1. Given Information:

    • Points A, F, D lie on one line.
    • Points B, F, E lie on another line.
    • The lines intersect at point F.
    • AFE=125\angle AFE = 125^\circ (Angle between AF and FE).
    • BFC=45\angle BFC = 45^\circ (Angle between BF and FC).
  2. Understand the Relationships:

    • The angles AFE\angle AFE and BFC\angle BFC are formed by the intersection of the two lines at point F.
    • These angles are related to each other by the geometry of the intersecting lines and the extended line from F to C.
  3. Analyze DFC\angle DFC:

    • DFC\angle DFC is formed between the line segment DFDF and the line segment FCFC.
    • Since BFC=45\angle BFC = 45^\circ, and considering the angle relationship around point F, we can deduce that DFC\angle DFC is supplementary to BFC\angle BFC.

    DFC+BFC=180\angle DFC + \angle BFC = 180^\circ Substituting the known value for BFC\angle BFC:

    DFC+45=180\angle DFC + 45^\circ = 180^\circ

    Solving for DFC\angle DFC:

    DFC=18045=135\angle DFC = 180^\circ - 45^\circ = 135^\circ

Final Answer: DFC=135\angle DFC = 135^\circ.


Would you like further clarification on any steps or concepts? Here are some related questions to explore:

  1. How does the concept of supplementary angles apply in this problem?
  2. What is the relationship between vertical angles and the angle pairs here?
  3. How can the angles around a point be used to solve other geometric problems?
  4. Why is the sum of angles on a straight line always 180°?
  5. Can this method be applied to any intersection of two lines, regardless of the angles given?

Tip: When dealing with intersecting lines, always check for supplementary or vertically opposite angle relationships. They can simplify the problem!

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Math Problem Analysis

Mathematical Concepts

Geometry
Angles
Supplementary Angles

Formulas

Supplementary angles: \( \angle DFC + \angle BFC = 180^\circ \)

Theorems

Supplementary Angle Theorem

Suitable Grade Level

Grades 7-9