Cosine Rule Problems - Solve Arbitrarily Chosen Triangles

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    Cosine Cosine rule
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Discussion Overview

The discussion revolves around the application of the law of cosines in solving problems involving arbitrarily chosen triangles. Participants explore the validity of selecting two sides and the included angle to determine the third side, as well as the implications of angle constraints.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant suggests that choosing sides a, b, and angle θ should allow for the calculation of side c using the law of cosines.
  • Another participant agrees and inquires about the reasoning behind any doubts regarding this approach.
  • Some participants note that the angle must be less than 180 degrees for the triangle to be valid.
  • There is a mention that if the angle exceeds this limit, it could lead to a triangle in the opposite direction, implying a need to adjust the sign in calculations.

Areas of Agreement / Disagreement

Participants generally agree that the law of cosines can be applied with the specified conditions, but there is some uncertainty regarding the implications of angles greater than 180 degrees and how they affect the triangle's validity.

Contextual Notes

Limitations include the assumption that the chosen angle is appropriate for forming a triangle and the potential for confusion when angles exceed 180 degrees, which may lead to different interpretations of the triangle's configuration.

nDever
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Hey,

If I wanted to make up problems that are solved using the law of cosines, shouldn't it work out even if I arbitrarily choose side a, b, and θ? After all, any two sides and an angle between them form a triangle. Correct?
 
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Yes correct. I'm curious to know why you think choosing sides a b and theta wouldn't give you an answer for c.
 
You're OK as long as the angle is < 180 deg.
 
mathman said:
You're OK as long as the angle is < 180 deg.

Even then you'd just have a triangle in the other direction. You would just have to change a sign(no pun intended).
 

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