Calculate Kite Area: Square Diagonal 36 cm² and AC = 2x

Kite Area with Square Diagonal Properties

ABCD is a kite.

BD is the diagonal of a square that has an area equal to 36 cm².

AC=2x AC=2x

Express the area of the kite in terms of X.

AAABBBCCCDDD

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Express the deltoid area using X
00:03 Draw a square whose diagonal is BD
00:12 Mark the square's side length as A
00:18 Use the formula for square area to find A
00:21 This is the size of A
00:26 Use the Pythagorean theorem to find BD
00:38 This is the size of BD
00:54 Now use the formula for deltoid area
00:58 (diagonal times diagonal) divided by 2
01:03 Substitute appropriate values and solve for the area
01:09 Simplify where possible
01:15 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

ABCD is a kite.

BD is the diagonal of a square that has an area equal to 36 cm².

AC=2x AC=2x

Express the area of the kite in terms of X.

AAABBBCCCDDD

2

Step-by-step solution

To solve this problem, we'll follow these steps:

  • Step 1: Calculate the side length of the square using the given area.
  • Step 2: Determine the length of BDBD using the side length.
  • Step 3: Use the kite area formula with diagonals BDBD and AC=2xAC=2x.

Now, let's work through each step:

Step 1: The area of the square is 36 cm². The side length of the square, denoted as ss, can be calculated by taking the square root of the area:

s=36=6 cms = \sqrt{36} = 6 \text{ cm}

Step 2: To find diagonal BDBD, we use the relationship for the diagonal of a square in terms of its side:

BD=s2BD = s \sqrt{2}. Given s=6s = 6, we compute:

BD=62 cmBD = 6\sqrt{2} \text{ cm}

Step 3: Now, we apply the formula for the area of a kite, which is 12×d1×d2\frac{1}{2} \times d1 \times d2, where d1=BD=62d1 = BD = 6\sqrt{2} and d2=AC=2xd2 = AC = 2x:

The area AA of the kite is:

A=12×62×2x=62x cm2A = \frac{1}{2} \times 6\sqrt{2} \times 2x = 6\sqrt{2}x \text{ cm}^2

Therefore, the area of the kite in terms of xx is 62x6\sqrt{2}x cm².

3

Final Answer

62x 6\sqrt{2}x cm²

Key Points to Remember

Essential concepts to master this topic
  • Square Diagonal: Diagonal equals side length multiplied by 2 \sqrt{2}
  • Technique: From area 36 cm², side = 6 cm, so BD = 62 6\sqrt{2} cm
  • Check: Area = 12×62×2x=62x \frac{1}{2} \times 6\sqrt{2} \times 2x = 6\sqrt{2}x cm² ✓

Common Mistakes

Avoid these frequent errors
  • Using the square's side length as the diagonal BD
    Don't use BD = 6 cm directly from the square's side = wrong answer 6x! The diagonal of a square is longer than its side. Always multiply the side length by 2 \sqrt{2} to get the diagonal: BD = 62 6\sqrt{2} cm.

Practice Quiz

Test your knowledge with interactive questions

Indicate the correct answer

The next quadrilateral is:

AAABBBCCCDDD

FAQ

Everything you need to know about this question

Why is the diagonal of a square not equal to its side length?

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A diagonal cuts across the square from corner to corner, creating a right triangle. Using the Pythagorean theorem with two sides of length 6: d2=62+62=72 d^2 = 6^2 + 6^2 = 72 , so d=72=62 d = \sqrt{72} = 6\sqrt{2} .

How do I know which diagonal is which in the kite?

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The problem tells us BD is the diagonal of a square, so BD has the special square property. AC is the other diagonal with length 2x 2x .

What's the formula for kite area again?

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Kite area = 12×d1×d2 \frac{1}{2} \times d_1 \times d_2 where d1 d_1 and d2 d_2 are the lengths of the two diagonals. The diagonals of a kite are always perpendicular!

Why don't we need to know the actual value of x?

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The question asks for the area in terms of x, meaning we leave x as a variable in our final answer. We express the relationship between the area and x: 62x 6\sqrt{2}x cm².

Can I simplify 62x 6\sqrt{2}x further?

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No, 62x 6\sqrt{2}x is already in its simplest form. You cannot combine the radical 2 \sqrt{2} with the other terms because they're different types of numbers.

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