Math Problem Statement

Determine the area of the quadrilateral whose vertices are A(-14, -2), B(10, 10), C(-10,-10), and D(4, -24). Use Area of a quadrilateral ABCD = Area of △ABC+ Area of △ACD

Solution

To determine the area of quadrilateral ABCDABCD using the method of dividing it into two triangles, we calculate the area of triangles ABCABC and ACDACD separately and then sum their areas.

1. Area of Triangle ABCABC

The vertices of triangle ABCABC are:

  • A(14,2)A(-14, -2)
  • B(10,10)B(10, 10)
  • C(10,10)C(-10, -10)

The area of a triangle given its vertices (x1,y1)(x_1, y_1), (x2,y2)(x_2, y_2), (x3,y3)(x_3, y_3) can be calculated using the formula:

AreaABC=12x1(y2y3)+x2(y3y1)+x3(y1y2)\text{Area}_{ABC} = \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 of points AA, BB, and CC:

AreaABC=12(14)(10(10))+10(10(2))+(10)(210)\text{Area}_{ABC} = \frac{1}{2} \left| (-14)(10 - (-10)) + 10(-10 - (-2)) + (-10)(-2 - 10) \right|

Simplify the expression:

AreaABC=12(14)(20)+10(8)+(10)(12)\text{Area}_{ABC} = \frac{1}{2} \left| (-14)(20) + 10(-8) + (-10)(-12) \right|

Calculate each term:

(14)(20)=280(-14)(20) = -280 10(8)=8010(-8) = -80 (10)(12)=120(-10)(-12) = 120

Add these up:

AreaABC=1228080+120=12240=12×240=120\text{Area}_{ABC} = \frac{1}{2} \left| -280 - 80 + 120 \right| = \frac{1}{2} \left| -240 \right| = \frac{1}{2} \times 240 = 120

So, the area of triangle ABCABC is 120120 square units.

2. Area of Triangle ACDACD

The vertices of triangle ACDACD are:

  • A(14,2)A(-14, -2)
  • C(10,10)C(-10, -10)
  • D(4,24)D(4, -24)

Using the same area formula for a triangle:

AreaACD=12x1(y2y3)+x2(y3y1)+x3(y1y2)\text{Area}_{ACD} = \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 of points AA, CC, and DD:

AreaACD=12(14)(10(24))+(10)(24(2))+4(2(10))\text{Area}_{ACD} = \frac{1}{2} \left| (-14)(-10 - (-24)) + (-10)(-24 - (-2)) + 4(-2 - (-10)) \right|

Simplify the expression:

AreaACD=12(14)(14)+(10)(22)+4(8)\text{Area}_{ACD} = \frac{1}{2} \left| (-14)(14) + (-10)(-22) + 4(8) \right|

Calculate each term:

(14)(14)=196(-14)(14) = -196 (10)(22)=220(-10)(-22) = 220 4(8)=324(8) = 32

Add these up:

AreaACD=12196+220+32=12×56=28\text{Area}_{ACD} = \frac{1}{2} \left| -196 + 220 + 32 \right| = \frac{1}{2} \times 56 = 28

So, the area of triangle ACDACD is 2828 square units.

3. Area of Quadrilateral ABCDABCD

Finally, sum the areas of triangles ABCABC and ACDACD to get the area of quadrilateral ABCDABCD:

AreaABCD=AreaABC+AreaACD=120+28=148\text{Area}_{ABCD} = \text{Area}_{ABC} + \text{Area}_{ACD} = 120 + 28 = 148

Thus, the area of the quadrilateral ABCDABCD is 148\boxed{148} square units.

Would you like further explanations or have any other questions?

Here are 5 questions related to this method:

  1. How can we verify the area calculated using a different method?
  2. What are the advantages of dividing a quadrilateral into triangles for area calculation?
  3. How would the area change if one of the vertices was shifted?
  4. How can the concept of vectors be used to find the area of the triangles?
  5. What would happen to the area calculation if one of the points was collinear with two others?

Tip: When dividing a quadrilateral into two triangles, ensure that the diagonal used divides the shape into two non-overlapping triangles for accurate area calculation.

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Math Problem Analysis

Mathematical Concepts

Geometry
Coordinate Geometry
Area of Triangles
Area of Quadrilaterals

Formulas

Area of a Triangle using Coordinates

Theorems

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Suitable Grade Level

Grades 9-12