Deltoid Area Calculation: Using 4cm and 5cm Diagonals

Deltoid Area with Incomplete Diagonal Information

Given the deltoid ABCD

The diagonal DB equals 5 cm

The diagonal AD equals 4 cm

Is it possible to calculate the area of the deltoid? If so, what is it?

444555AAABBBCCCDDD

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Can we calculate the area of the rhombus? And if so, what is it?
00:03 We will use the formula for calculating the area of a rhombus
00:09 (diagonal multiplied by diagonal) divided by 2
00:19 We only know one diagonal
00:30 Therefore, we have no way to calculate the area of the rhombus
00:37 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

Given the deltoid ABCD

The diagonal DB equals 5 cm

The diagonal AD equals 4 cm

Is it possible to calculate the area of the deltoid? If so, what is it?

444555AAABBBCCCDDD

2

Step-by-step solution

To determine whether we can calculate the area of the deltoid ABCD, we initially examine information about its diagonals. The area formula for a kite, i.e., A=12×d1×d2 A = \frac{1}{2} \times d_1 \times d_2 , where d1 d_1 and d2 d_2 are the two diagonals intersecting at right angles, cannot be straightforwardly applied here. Without assurance of these diagonals being perpendicular, and since no side lengths or further diagonal intersection properties (like angles) are given, we lack the prerequisite conditions or known properties to substantiate an area calculation. Furthermore, only possessing the lengths of DB=5cm DB = 5 \, \text{cm} and AD=4cm AD = 4 \, \text{cm} restricts our approach.

Therefore, given we cannot sufficiently confirm all necessary conditions, it is not possible to determine the area of the deltoid from the provided data alone.

3

Final Answer

It is not possible to

Key Points to Remember

Essential concepts to master this topic
  • Area Rule: Deltoids need perpendicular diagonals and their full lengths
  • Formula Check: A=12×d1×d2 A = \frac{1}{2} \times d_1 \times d_2 requires both complete diagonals
  • Verification: Confirm diagonals are perpendicular and complete before calculating ✓

Common Mistakes

Avoid these frequent errors
  • Assuming any two diagonal measurements give the area
    Don't use A=12×4×5=10 cm2 A = \frac{1}{2} \times 4 \times 5 = 10 \text{ cm}^2 without checking perpendicularity! The formula only works when diagonals intersect at right angles and you have their complete lengths. Always verify the diagonals are perpendicular and that you have the full diagonal lengths, not just segments.

Practice Quiz

Test your knowledge with interactive questions

Look at the kite ABCD below.

Diagonal DB = 10

CB = 4

Is it possible to calculate the area of the kite? If so, what is it?

444101010AAADDDCCCBBB

FAQ

Everything you need to know about this question

Why can't I just multiply 4 cm and 5 cm to get the area?

+

The formula A=12×d1×d2 A = \frac{1}{2} \times d_1 \times d_2 only works when the diagonals are perpendicular and you have their complete lengths. Without confirming these conditions, the calculation is invalid.

What makes a deltoid different from other quadrilaterals?

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A deltoid (or kite) has two pairs of adjacent equal sides. Its diagonals are perpendicular, but only one diagonal is bisected by the other - this is crucial for area calculations!

How do I know if the diagonals are perpendicular?

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In a deltoid, diagonals are always perpendicular by definition. However, you need the complete diagonal lengths, not just segments like AD = 4 cm, to use the area formula.

What information would I need to calculate the deltoid's area?

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You need either:

  • Both complete diagonal lengths (since they're perpendicular)
  • Side lengths and angles to use other area formulas
  • Height and base measurements

Is AD = 4 cm a complete diagonal?

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No! Looking at the diagram, AD appears to be just part of a diagonal, not a complete diagonal from one vertex to the opposite vertex. Complete diagonals would be AC and BD.

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