Math Problem Statement

In a right-angled triangle A B C ABC with ∠ B

9 0 ∘ ∠B=90 ∘ , the length of side A B AB = 8 8 units and the length of side B C BC = 6 6 units. Point D D is on side A C AC such that A D : D C

2 : 3 AD:DC=2:3. Point E E is on side B C BC such that B E : E C

3 : 4 BE:EC=3:4. If the area of triangle B D E BDE is maximized, what is the ratio of the areas of triangles B D E BDE and A B C ABC?

In a right-angled triangle ABC with ∠B = 90°, the length of side AB = 8 units and the length of side BC = 6 units. Point D is on side AC such that AD : DC = 2 : 3. Point E is on side BC such that BE : EC = 3 : 4. If the area of triangle BDE is maximized, what is the ratio of the areas of triangles BDE and ABC?

Solution

Let's solve this step-by-step.

Step 1: Determine the Coordinates of Points

  1. Triangle ABC is a right-angled triangle at BB, with AB=8AB = 8 units and BC=6BC = 6 units.
  2. Place BB at the origin (0,0)(0, 0).
  3. Let AA be at (8,0)(8, 0) (since AB=8AB = 8).
  4. Let CC be at (0,6)(0, 6) (since BC=6BC = 6).

Step 2: Locate Point DD on ACAC

  1. Since DD divides ACAC in the ratio AD:DC=2:3AD : DC = 2 : 3, use the section formula.
  2. Coordinates of DD (using (x1,y1)=(8,0)(x_1, y_1) = (8, 0) for AA and (x2,y2)=(0,6)(x_2, y_2) = (0, 6) for CC): D=(20+382+3,26+302+3)=(245,125)D = \left( \frac{2 \cdot 0 + 3 \cdot 8}{2 + 3}, \frac{2 \cdot 6 + 3 \cdot 0}{2 + 3} \right) = \left( \frac{24}{5}, \frac{12}{5} \right)

Step 3: Locate Point EE on BCBC

  1. EE divides BCBC in the ratio BE:EC=3:4BE : EC = 3 : 4.
  2. Coordinates of EE (using (x1,y1)=(0,0)(x_1, y_1) = (0, 0) for BB and (x2,y2)=(0,6)(x_2, y_2) = (0, 6) for CC): E=(30+403+4,36+403+4)=(0,187)E = \left( \frac{3 \cdot 0 + 4 \cdot 0}{3 + 4}, \frac{3 \cdot 6 + 4 \cdot 0}{3 + 4} \right) = \left( 0, \frac{18}{7} \right)

Step 4: Calculate the Area of ABC\triangle ABC

Since ABC\triangle ABC is a right triangle with base AB=8AB = 8 and height BC=6BC = 6, Area of ABC=12×8×6=24\text{Area of } \triangle ABC = \frac{1}{2} \times 8 \times 6 = 24

Step 5: Calculate the Area of BDE\triangle BDE

Using vertices B=(0,0)B = (0, 0), D=(245,125)D = \left(\frac{24}{5}, \frac{12}{5}\right), and E=(0,187)E = \left(0, \frac{18}{7}\right), apply the area formula for a triangle given vertices (x1,y1)(x_1, y_1), (x2,y2)(x_2, y_2), and (x3,y3)(x_3, y_3): Area=12x1(y2y3)+x2(y3y1)+x3(y1y2)\text{Area} = \frac{1}{2} \left| x_1(y_2 - y_3) + x_2(y_3 - y_1) + x_3(y_1 - y_2) \right| Substitute the coordinates: Area of BDE=120(125187)+245(1870)+0(0125)\text{Area of } \triangle BDE = \frac{1}{2} \left| 0 \cdot \left(\frac{12}{5} - \frac{18}{7}\right) + \frac{24}{5} \cdot \left(\frac{18}{7} - 0\right) + 0 \cdot \left(0 - \frac{12}{5}\right) \right| This simplifies to: =12245187=1243235=21635= \frac{1}{2} \left| \frac{24}{5} \cdot \frac{18}{7} \right| = \frac{1}{2} \cdot \frac{432}{35} = \frac{216}{35}

Step 6: Find the Ratio of the Areas of BDE\triangle BDE and ABC\triangle ABC

Ratio=Area of BDEArea of ABC=2163524=21635×24=216840=935\text{Ratio} = \frac{\text{Area of } \triangle BDE}{\text{Area of } \triangle ABC} = \frac{\frac{216}{35}}{24} = \frac{216}{35 \times 24} = \frac{216}{840} = \frac{9}{35}

Final Answer

The ratio of the areas of triangles BDEBDE and ABCABC is: 935\boxed{\frac{9}{35}}

Would you like a further breakdown or additional questions related to this problem?

Related Questions

  1. How do you apply the section formula for internal division?
  2. What is the significance of maximizing the area in such geometric problems?
  3. How do you calculate the area of a triangle given vertices?
  4. What are some other methods to find the area of a triangle besides base and height?
  5. How does changing the ratio AD:DCAD : DC affect the area of BDE\triangle BDE?

Tip

In coordinate geometry, using section and area formulas often simplifies problems involving division points and area calculations of triangles.

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Math Problem Analysis

Mathematical Concepts

Coordinate Geometry
Area of Triangle
Ratios
Section Formula

Formulas

Area of a triangle given vertices: Area = 1/2 * | x1(y2 - y3) + x2(y3 - y1) + x3(y1 - y2) |
Section formula for dividing a line segment internally in a given ratio

Theorems

Coordinate Geometry - Section Formula

Suitable Grade Level

Grades 10-12