Area of triangle inside parallelogram

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SUMMARY

The discussion centers on calculating the area of triangle PQD within a parallelogram using the formula A = 1/2 * a * b * sin(C) and Heron's formula A = √(s(s-a)(s-b)(s-c)). The user attempts to derive the side lengths a, b, and c based on given areas but struggles with the relationship between the angles. A suggestion is made that the angles may not be relevant, as the ratios remain consistent regardless of their values.

PREREQUISITES
  • Understanding of triangle area formulas, specifically A = 1/2 * a * b * sin(C)
  • Familiarity with Heron's formula for triangle area calculation
  • Basic knowledge of geometry, particularly properties of parallelograms
  • Ability to manipulate algebraic expressions involving trigonometric functions
NEXT STEPS
  • Research the properties of triangles within parallelograms
  • Study the implications of angle independence in triangle area calculations
  • Explore advanced applications of Heron's formula in complex geometric shapes
  • Learn about the relationships between side lengths and angles in triangles
USEFUL FOR

Students studying geometry, particularly those tackling problems involving triangles within parallelograms, as well as educators looking for insights into teaching area calculations.

cjwalle
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Homework Statement



http://folk.uio.no/robinbj/gg/ggstart.pdf"
I am supposed to find the area of the triangle PQD. The numbers given are the areas of the other triangles.

Homework Equations


A= \frac{1}{2} a b \sin{C}

As well as Heron's formula, possibly?
A= \sqrt{s(s-a)(s-b)(s-c)} where s = \frac{a+b+c}{2}

The Attempt at a Solution


Where I'm stumped is exactly how to start. At first, I figured I'd try to find the values of a, b and c. Using the area of a triangle:

a = DP = \frac{14}{AP\sin{\theta}}

Similarly, for b:

b = QP = \frac{56}{QB\sin{\alpha}}

And c:

c = QD = \frac{28}{QC\sin{x}}

Meaning that s = \frac{7}{AP\sin{\theta}} + \frac{28}{QB\sin{\alpha}} + \frac{14}{QC\sin{x}}

However, dealing with three different angles, without knowing the relationship between them or the sum of the angles, I just don't know how to proceed and solve the exercise based on this. I am not looking for a solution from you guys, mind you. Just a tip to get me on the right track?

Thank you.
 
Last edited by a moderator:
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Hi cjwalle! :smile:

I don't think the angles matter …

won't the ratios be the same, whatever the angles are, so you might as well make it a square?
 

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