Solving a Law of Cosines Problem: Finding the Length of a Side

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SUMMARY

The discussion focuses on solving a Law of Cosines problem to find the length of a side in a parallelogram. The user successfully applied the Law of Cosines formula, specifically using the equation d² = a² + b² - 2ab cos(30°), resulting in d = 3.23. The user initially struggled but gained clarity by recalling the properties of parallelograms, particularly the relationships between opposite angles and the sum of angles. This understanding simplified the problem significantly.

PREREQUISITES
  • Understanding of the Law of Cosines
  • Basic properties of parallelograms
  • Knowledge of trigonometric functions, specifically cosine
  • Ability to manipulate algebraic equations
NEXT STEPS
  • Study the derivation and applications of the Law of Cosines in various geometric problems
  • Explore the properties of parallelograms in depth, including angle relationships
  • Learn about other trigonometric identities and their applications in geometry
  • Practice solving problems involving the Law of Cosines with different angle measures
USEFUL FOR

Students studying geometry, particularly those tackling problems involving the Law of Cosines and properties of parallelograms.

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Homework Statement



[PLAIN]http://img28.imageshack.us/img28/1046/mathproblemp.jpg

Homework Equations



Law of Cosines

The Attempt at a Solution



I'm not really sure what to do for this problem, it looks easy but I can't figure it out. I tried # 11 and was able to find d.

d2=a2+b2-2(a)(b)cos(30)
d=3.23

However, I don't know where to go from there.
 
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Hints:

1. What do you know about the angles of the opposite corners of a parallelogram?
2. What do you know about the sum of the angles of a parallelogram?
 
Ahh... thanks, I didn't know the basic properties of parallelograms. Now this problem is much easier.
 

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