Find angle of a triangle with given sides

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Homework Help Overview

The discussion revolves around finding the angle of triangle ABC given its sides: AB=7, BC=8, and CA=9. The original poster expresses uncertainty about how to calculate angle B, despite having a numerical answer.

Discussion Character

  • Exploratory, Conceptual clarification

Approaches and Questions Raised

  • Some participants suggest using the cosine rule as a method to find the angle. Others mention the need for a calculator to compute the cosine value and obtain the angle to three significant figures.

Discussion Status

Participants are exploring the cosine rule and its application to the problem. There is acknowledgment of the need for a calculator, and some light-hearted commentary on the existence of mathematical rules. No explicit consensus has been reached regarding the approach.

Contextual Notes

The original poster appears to be looking for guidance on the calculation process without prior knowledge of the cosine rule. There is an implication of homework constraints, as the poster seeks help without being provided a direct solution.

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In a triangle ABC, AB=7, BC=8, CA=9, find angle B correct to 3 significant figures.
The answer is 73.4, but i don't know how to calculate it, thanks.
 
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Use the cosine rule.
 
U'll need a calculator to compute B,i.e.solve the equation

[tex]\cos B=value[/tex]

and select the first 3 decimals the calculator shows u...

Daniel.
 
O, I forgot there is a rule called " cosine rule" in the world, thanks.
 
The world hath many rules, none of which you ought to ignore..:wink:
 

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