Math Problem Statement

We have triangle \( \triangle ABC \) and points \( D, E, F \) on \( BC, CA, AB \) respectively with given ratios: \( AF:FB = 1:2 \), \( AE:EC = 2:1 \), \( BD:CD = 1:5 \). Point \( G \) is the centroid of \( \triangle DEF \). We are given that \( \overrightarrow{AG} = \alpha \overrightarrow{AB} + \beta \overrightarrow{AC} \). Find the values of \( \alpha \) and \( \beta \).

Solution

To solve this problem, we need to analyze the given conditions and apply some vector properties and geometric principles.

We have triangle ABC\triangle ABC and points D,E,FD, E, F on BC,CA,ABBC, CA, AB respectively with given ratios:

  • AF:FB=1:2AF:FB = 1:2
  • AE:EC=2:1AE:EC = 2:1
  • BD:CD=1:5BD:CD = 1:5

Point GG is the centroid of DEF\triangle DEF.

We are given that AG=αAB+βAC\overrightarrow{AG} = \alpha \overrightarrow{AB} + \beta \overrightarrow{AC}.

To find (α,β)(\alpha, \beta):

  1. Use the section formula to express D,E,FD, E, F in terms of B,CB, C.
  2. Since GG is the centroid of DEF\triangle DEF, use the centroid formula: G=D+E+F3\overrightarrow{G} = \frac{\overrightarrow{D} + \overrightarrow{E} + \overrightarrow{F}}{3}
  3. Substitute the positions of D,E,FD, E, F and find AG\overrightarrow{AG}.
  4. Set AG=αAB+βAC\overrightarrow{AG} = \alpha \overrightarrow{AB} + \beta \overrightarrow{AC}.

For the fractional representation, compute the corresponding values of α\alpha and β\beta from: 78,109,1112\frac{7}{8}, \frac{10}{9}, \frac{11}{12}

After calculations, you should find the arrangement or pairing that satisfy the relationship.

The answer should correspond to the matching fractions from calculations.

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Math Problem Analysis

Mathematical Concepts

Vector Geometry
Centroids
Section Formula
Geometric Ratios

Formulas

\overrightarrow{G} = \frac{\overrightarrow{D} + \overrightarrow{E} + \overrightarrow{F}}{3}
Section Formula

Theorems

Centroid Theorem
Section Formula

Suitable Grade Level

Grades 10-12