Proving Law of Sines Using Vector Cross Product

In summary, the law of sines can be proven by using the vector cross product and considering the area of the triangle. By setting A+B+C=0 and using the equation |A||C|sin ( θ ) = (a2c3 − a3c2) + (a3c1 − a1c3) + (a1c2 − a2c1), the proof can be derived. The attempt at a solution involved using .5 |a||c|sin \theta and trying different forms of the cross product, but it was eventually figured out.
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Homework Statement


Prove the law of sines using a vector cross product. (Hint, consider the area of the triangle and that A+B+C=0.)


Homework Equations


|A||C|sin ( θ ) = (a2c3 − a3c2) + (a3c1 − a1c3) + (a1c2 − a2c1)


The Attempt at a Solution


The farthest I went is to show .5 |a||c|sin \theta .. I've tried some other things but then it just turns out to be some incomprehensible mess. I chose C to be my longest side. I simply do not know what to do; I've exhausted both forms of the cross product I know, and it appers to go nowhere.
 
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  • #2
Never mind, I figured it out. Thanks anyway!
 

Related to Proving Law of Sines Using Vector Cross Product

1. What is the Law of Sines?

The Law of Sines is a trigonometric rule that relates the sides and angles of a triangle. It states that the ratio of the length of a side of a triangle to the sine of the opposite angle is the same for all three sides.

2. How is the Law of Sines typically proven?

The Law of Sines is typically proven using geometry and the properties of similar triangles. It can also be proven using the Law of Cosines or the Pythagorean Theorem.

3. What is the role of the vector cross product in proving the Law of Sines?

The vector cross product is used to determine the area of a triangle in 3-dimensional space. This area can then be used to prove the Law of Sines.

4. Can the Law of Sines be proven using only the vector cross product?

No, the Law of Sines cannot be proven using only the vector cross product. It is just one of the tools used in the proof, along with geometry and other trigonometric principles.

5. Are there any limitations to using the vector cross product to prove the Law of Sines?

The vector cross product method may not be the most efficient or straightforward way to prove the Law of Sines. It also may not be applicable in all situations, such as when dealing with non-planar triangles or when the angles are greater than 180 degrees.

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