Calculate Square Perimeter Using Diagonal Expression: 3√2×(3²-2³)-2√2

Square Properties with Diagonal Calculations

ABCD is a square.

The length of the diagonal:
32×(3223)22 3\sqrt{2}\times\left(3^2-2^3\right)-2\sqrt{2}

AAABBBCCCDDDWhat is the perimeter of the square ABCD?

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Determine the perimeter of the square
00:05 In a square all sides are equal, we'll mark them as A
00:08 In a square all angles are right angles
00:11 Use the Pythagorean theorem in triangle ADB
00:21 Substitute appropriate values into the formula according to the given values and solve for A
00:44 Solve the powers and substitute
00:59 Always solve parentheses first
01:20 Subtract
01:23 The square root of any number squared equals the number itself
01:26 Isolate side A
01:34 This is the length of side A
01:41 The perimeter of a square equals 4 times the side (because all sides are equal)
01:47 Substitute in the length A that we found and solve for the perimeter
01:50 This is the solution

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

ABCD is a square.

The length of the diagonal:
32×(3223)22 3\sqrt{2}\times\left(3^2-2^3\right)-2\sqrt{2}

AAABBBCCCDDDWhat is the perimeter of the square ABCD?

2

Step-by-step solution

The problem involves the square ABCD, and we need to determine its perimeter, given the expression for the length of its diagonal. Here's the step-by-step solution:

Let's denote the side of the square ABCD as s s . The diagonal of a square can be calculated using Pythagoras' theorem as:

  • d=s2 d = s\sqrt{2}

The problem provides an expression for the length of the diagonal:

  • 32×(3223)22 3\sqrt{2}\times(3^2-2^3)-2\sqrt{2}

Let's simplify this expression step by step.

First, calculate the powers:

  • 32=9 3^2 = 9

  • 23=8 2^3 = 8

Subtract these values:

  • 3223=98=1 3^2 - 2^3 = 9 - 8 = 1

Substitute back into the expression for the diagonal:

  • 32×122 3\sqrt{2} \times 1 - 2\sqrt{2}

This simplifies to:

  • 3222 3\sqrt{2} - 2\sqrt{2}

  • (32)2=12=2 (3 - 2)\sqrt{2} = 1\sqrt{2} = \sqrt{2}

So, the length of the diagonal is 2 \sqrt{2} .

We know from the formula for the diagonal of a square that d=s2 d = s\sqrt{2} . Given d=2 d = \sqrt{2} , we can equate:

  • s2=2 s\sqrt{2} = \sqrt{2}

Thus:

  • s=1 s = 1

Therefore, the perimeter of the square ABCD is:

  • 4×s=4×1=4 4 \times s = 4 \times 1 = 4

Hence, the perimeter of the square ABCD is 4.

3

Final Answer

4

Key Points to Remember

Essential concepts to master this topic
  • Diagonal Formula: For any square with side s, diagonal equals s2 s\sqrt{2}
  • Order of Operations: Calculate powers first: 32=9 3^2 = 9 and 23=8 2^3 = 8
  • Verification: Check that 1×2=2 1 \times \sqrt{2} = \sqrt{2} matches diagonal expression ✓

Common Mistakes

Avoid these frequent errors
  • Forgetting order of operations in complex expressions
    Don't calculate 32×32 3\sqrt{2} \times 3^2 before evaluating the parentheses = wrong diagonal length! This ignores PEMDAS rules. Always evaluate parentheses first, then powers, then multiply and subtract from left to right.

Practice Quiz

Test your knowledge with interactive questions

What is the result of the following equation?

\( 36-4\div2 \)

FAQ

Everything you need to know about this question

Why does a square's diagonal equal s2 s\sqrt{2} ?

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This comes from the Pythagorean theorem! In a square, the diagonal forms the hypotenuse of a right triangle with two equal sides. So d2=s2+s2=2s2 d^2 = s^2 + s^2 = 2s^2 , which means d=s2 d = s\sqrt{2} .

Do I need to simplify 3222 3\sqrt{2} - 2\sqrt{2} first?

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Yes! These are like terms because they both have 2 \sqrt{2} . Combine them: (32)2=12=2 (3-2)\sqrt{2} = 1\sqrt{2} = \sqrt{2} .

What if I calculated 3223 3^2 - 2^3 wrong?

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Double-check: 32=3×3=9 3^2 = 3 \times 3 = 9 and 23=2×2×2=8 2^3 = 2 \times 2 \times 2 = 8 . So 98=1 9 - 8 = 1 . Any other result will give you the wrong diagonal length!

How do I find the side length from the diagonal?

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Use the diagonal formula backwards! If d=s2 d = s\sqrt{2} , then s=d2 s = \frac{d}{\sqrt{2}} . In this problem: s=22=1 s = \frac{\sqrt{2}}{\sqrt{2}} = 1 .

Why is the perimeter 4 times the side length?

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A square has 4 equal sides, so perimeter = 4 × side length. With side length 1, the perimeter is 4×1=4 4 \times 1 = 4 .

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