Proving (A X B) X C = AxBxCx (i x k) + AyBxCy (j x k) | Unit Vectors

So the two sides aren't equal to each other.In summary, the statement asks to prove that (A X B) X C is equal to the expression AxBxCx (i x k) + AyBxCy (j x k), where i, j, and k are unit vectors. The attempt at a solution involves simplifying the left-hand side and then expanding the right-hand side, but there is a mistake in the simplification and the two sides are not equal for all values of A, B, and C.
  • #1
abrowaqas
114
0

Homework Statement


Prove that
(A X B) X C = AxBxCx (i x k) + AyBxCy (j x k)
where i , j and k are unit vectors ?


Homework Equations





The Attempt at a Solution



let A= Axi+Ayj
B= Bxi+Byj

L.H.S = (AXB)XC
= (C.A) B - (C.B) A
= (AxCx+AyCy)(Bxi+Byj)- (BxCx+ByCy)(Axi+Ayj)
after simplification we get
= AxByCx i - AxByCy j + AyBxCy i - AyBxCx j
there i am held up... now how i proceed further..
 
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  • #2
I believe you should start by writing A and B has 3 dimensional vectors rather than 2. I would follow the exact steps you have above and then finish the problem by expanding the RHS (AxBxCx (i x k) + AyBxCy (j x k)) and showing that the two are equivalent.
 
  • #3
abrowaqas said:

Homework Statement


Prove that
(A X B) X C = AxBxCx (i x k) + AyBxCy (j x k)
where i , j and k are unit vectors ?
It doesn't work for A=i, B=j, and C=i. Since Bx=0, the righthand side is equal to 0, but the lefthand side is equal to j.
 

Related to Proving (A X B) X C = AxBxCx (i x k) + AyBxCy (j x k) | Unit Vectors

1. What is the purpose of proving (A X B) X C = AxBxCx (i x k) + AyBxCy (j x k) | Unit Vectors?

The purpose of proving this equation is to demonstrate the mathematical relationship between the cross product of three vectors (A, B, and C) and the dot product of those vectors with the unit vectors (i, j, and k).

2. How is the cross product of three vectors calculated?

The cross product of three vectors is calculated by taking the determinant of a 3x3 matrix composed of the three vectors and the unit vectors. This results in a new vector that is perpendicular to the original three vectors.

3. Why is the cross product important in vector calculations?

The cross product is important in vector calculations because it allows us to find a vector that is perpendicular to two given vectors. This can be useful in many applications, such as calculating torque or determining the direction of a magnetic field.

4. How can this equation be applied in real-world situations?

This equation can be applied in many real-world situations, such as calculating the torque exerted by a force on an object, determining the direction of a magnetic field, or finding the angular momentum of a rotating object.

5. Are there any limitations to this equation?

One limitation of this equation is that it only applies to three-dimensional vectors. It also assumes that the vectors are perpendicular to each other. Additionally, this equation only works for unit vectors, so it may not be applicable in all situations.

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