The given identities are verified by using operations of the del operator such as divergence and curl of the given vectors.
<h3>What are the divergence and curl of a vector field?</h3>
The del operator is used for finding the divergence and the curl of a vector field.
The del operator is given by
![\nabla=\^i\frac{\partial}{\partial x}+\^j \frac{\partial}{\partial y}+\^k\frac{\partial}{\partial z}](https://tex.z-dn.net/?f=%5Cnabla%3D%5C%5Ei%5Cfrac%7B%5Cpartial%7D%7B%5Cpartial%20x%7D%2B%5C%5Ej%20%5Cfrac%7B%5Cpartial%7D%7B%5Cpartial%20y%7D%2B%5C%5Ek%5Cfrac%7B%5Cpartial%7D%7B%5Cpartial%20z%7D)
Consider a vector field ![F=x\^i+y\^j+z\^k](https://tex.z-dn.net/?f=F%3Dx%5C%5Ei%2By%5C%5Ej%2Bz%5C%5Ek)
Then the divergence of the vector F is,
div F =
= ![(\^i\frac{\partial}{\partial x}+\^j \frac{\partial}{\partial y}+\^k\frac{\partial}{\partial z}).(x\^i+y\^j+z\^k)](https://tex.z-dn.net/?f=%28%5C%5Ei%5Cfrac%7B%5Cpartial%7D%7B%5Cpartial%20x%7D%2B%5C%5Ej%20%5Cfrac%7B%5Cpartial%7D%7B%5Cpartial%20y%7D%2B%5C%5Ek%5Cfrac%7B%5Cpartial%7D%7B%5Cpartial%20z%7D%29.%28x%5C%5Ei%2By%5C%5Ej%2Bz%5C%5Ek%29)
and the curl of the vector F is,
curl F =
= ![\^i(\frac{\partial Fz}{\partial y}- \frac{\partial Fy}{\partial z})+\^j(\frac{\partial Fx}{\partial z}-\frac{\partial Fz}{\partial x})+\^k(\frac{\partial Fy}{\partial x}-\frac{\partial Fx}{\partial y})](https://tex.z-dn.net/?f=%5C%5Ei%28%5Cfrac%7B%5Cpartial%20Fz%7D%7B%5Cpartial%20y%7D-%20%5Cfrac%7B%5Cpartial%20Fy%7D%7B%5Cpartial%20z%7D%29%2B%5C%5Ej%28%5Cfrac%7B%5Cpartial%20Fx%7D%7B%5Cpartial%20z%7D-%5Cfrac%7B%5Cpartial%20Fz%7D%7B%5Cpartial%20x%7D%29%2B%5C%5Ek%28%5Cfrac%7B%5Cpartial%20Fy%7D%7B%5Cpartial%20x%7D-%5Cfrac%7B%5Cpartial%20Fx%7D%7B%5Cpartial%20y%7D%29)
<h3>Calculation:</h3>
The given vector fields are:
and ![F2 = Q\^i + R\^j + S\^k](https://tex.z-dn.net/?f=F2%20%3D%20Q%5C%5Ei%20%2B%20R%5C%5Ej%20%2B%20S%5C%5Ek)
1) Verifying the identity: ![\nabla.(aF1+bF2)=a\nabla.F1+b\nabla.F2](https://tex.z-dn.net/?f=%5Cnabla.%28aF1%2BbF2%29%3Da%5Cnabla.F1%2Bb%5Cnabla.F2)
Consider L.H.S
⇒ ![\nabla.(aF1+bF2)](https://tex.z-dn.net/?f=%5Cnabla.%28aF1%2BbF2%29)
⇒ ![\nabla.(a(M\^i + N\^j + P\^k) + b(Q\^i + R\^j + S\^k))](https://tex.z-dn.net/?f=%5Cnabla.%28a%28M%5C%5Ei%20%2B%20N%5C%5Ej%20%2B%20P%5C%5Ek%29%20%2B%20b%28Q%5C%5Ei%20%2B%20R%5C%5Ej%20%2B%20S%5C%5Ek%29%29)
⇒ ![\nabla.((aM+bQ)\^i+(aN+bR)\^j+(aP+bS)\^k)](https://tex.z-dn.net/?f=%5Cnabla.%28%28aM%2BbQ%29%5C%5Ei%2B%28aN%2BbR%29%5C%5Ej%2B%28aP%2BbS%29%5C%5Ek%29)
⇒ ![(\^i\frac{\partial}{\partial x}+\^j \frac{\partial}{\partial y}+\^k\frac{\partial}{\partial z}).((aM+bQ)\^i+(aN+bR)\^j+(aP+bS)\^k)](https://tex.z-dn.net/?f=%28%5C%5Ei%5Cfrac%7B%5Cpartial%7D%7B%5Cpartial%20x%7D%2B%5C%5Ej%20%5Cfrac%7B%5Cpartial%7D%7B%5Cpartial%20y%7D%2B%5C%5Ek%5Cfrac%7B%5Cpartial%7D%7B%5Cpartial%20z%7D%29.%28%28aM%2BbQ%29%5C%5Ei%2B%28aN%2BbR%29%5C%5Ej%2B%28aP%2BbS%29%5C%5Ek%29)
Applying the dot product between these two vectors,
⇒
...(1)
Consider R.H.S
⇒ ![a\nabla.F1+b\nabla.F2](https://tex.z-dn.net/?f=a%5Cnabla.F1%2Bb%5Cnabla.F2)
So,
![\nabla.F1=(\^i\frac{\partial}{\partial x}+\^j \frac{\partial}{\partial y}+\^k\frac{\partial}{\partial z}).(M\^i + N\^j + P\^k)](https://tex.z-dn.net/?f=%5Cnabla.F1%3D%28%5C%5Ei%5Cfrac%7B%5Cpartial%7D%7B%5Cpartial%20x%7D%2B%5C%5Ej%20%5Cfrac%7B%5Cpartial%7D%7B%5Cpartial%20y%7D%2B%5C%5Ek%5Cfrac%7B%5Cpartial%7D%7B%5Cpartial%20z%7D%29.%28M%5C%5Ei%20%2B%20N%5C%5Ej%20%2B%20P%5C%5Ek%29)
⇒ ![\nabla.F1=\frac{\partial M}{\partial x}+\frac{\partial N}{\partial y}+\frac{\partial P}{\partial z}](https://tex.z-dn.net/?f=%5Cnabla.F1%3D%5Cfrac%7B%5Cpartial%20M%7D%7B%5Cpartial%20x%7D%2B%5Cfrac%7B%5Cpartial%20N%7D%7B%5Cpartial%20y%7D%2B%5Cfrac%7B%5Cpartial%20P%7D%7B%5Cpartial%20z%7D)
![\nabla.F2=(\^i\frac{\partial}{\partial x}+\^j \frac{\partial}{\partial y}+\^k\frac{\partial}{\partial z}).(Q\^i + R\^j + S\^k)](https://tex.z-dn.net/?f=%5Cnabla.F2%3D%28%5C%5Ei%5Cfrac%7B%5Cpartial%7D%7B%5Cpartial%20x%7D%2B%5C%5Ej%20%5Cfrac%7B%5Cpartial%7D%7B%5Cpartial%20y%7D%2B%5C%5Ek%5Cfrac%7B%5Cpartial%7D%7B%5Cpartial%20z%7D%29.%28Q%5C%5Ei%20%2B%20R%5C%5Ej%20%2B%20S%5C%5Ek%29)
⇒ ![\nabla.F1=\frac{\partial Q}{\partial x}+\frac{\partial R}{\partial y}+\frac{\partial S}{\partial z}](https://tex.z-dn.net/?f=%5Cnabla.F1%3D%5Cfrac%7B%5Cpartial%20Q%7D%7B%5Cpartial%20x%7D%2B%5Cfrac%7B%5Cpartial%20R%7D%7B%5Cpartial%20y%7D%2B%5Cfrac%7B%5Cpartial%20S%7D%7B%5Cpartial%20z%7D)
Then,
![a\nabla.F1+b\nabla.F2=a(\frac{\partial M}{\partial x}+\frac{\partial N}{\partial y}+\frac{\partial P}{\partial z})+b(\frac{\partial Q}{\partial x}+\frac{\partial R}{\partial y}+\frac{\partial S}{\partial z})](https://tex.z-dn.net/?f=a%5Cnabla.F1%2Bb%5Cnabla.F2%3Da%28%5Cfrac%7B%5Cpartial%20M%7D%7B%5Cpartial%20x%7D%2B%5Cfrac%7B%5Cpartial%20N%7D%7B%5Cpartial%20y%7D%2B%5Cfrac%7B%5Cpartial%20P%7D%7B%5Cpartial%20z%7D%29%2Bb%28%5Cfrac%7B%5Cpartial%20Q%7D%7B%5Cpartial%20x%7D%2B%5Cfrac%7B%5Cpartial%20R%7D%7B%5Cpartial%20y%7D%2B%5Cfrac%7B%5Cpartial%20S%7D%7B%5Cpartial%20z%7D%29)
⇒
...(2)
From (1) and (2),
![\nabla.(aF1+bF2)=a\nabla.F1+b\nabla.F2](https://tex.z-dn.net/?f=%5Cnabla.%28aF1%2BbF2%29%3Da%5Cnabla.F1%2Bb%5Cnabla.F2)
2) Verifying the identity: ![\nabla\times(aF1+bF2)=a\nabla\times F1+b\nabla\times F2](https://tex.z-dn.net/?f=%5Cnabla%5Ctimes%28aF1%2BbF2%29%3Da%5Cnabla%5Ctimes%20F1%2Bb%5Cnabla%5Ctimes%20F2)
Consider L.H.S
⇒ ![\nabla\times(aF1+bF2)](https://tex.z-dn.net/?f=%5Cnabla%5Ctimes%28aF1%2BbF2%29)
⇒ ![(\^i\frac{\partial}{\partial x}+\^j \frac{\partial}{\partial y}+\^k\frac{\partial}{\partial z})\times(a(M\^i+N\^j+P\^k)+b(Q\^i+R\^j+S\^k))](https://tex.z-dn.net/?f=%28%5C%5Ei%5Cfrac%7B%5Cpartial%7D%7B%5Cpartial%20x%7D%2B%5C%5Ej%20%5Cfrac%7B%5Cpartial%7D%7B%5Cpartial%20y%7D%2B%5C%5Ek%5Cfrac%7B%5Cpartial%7D%7B%5Cpartial%20z%7D%29%5Ctimes%28a%28M%5C%5Ei%2BN%5C%5Ej%2BP%5C%5Ek%29%2Bb%28Q%5C%5Ei%2BR%5C%5Ej%2BS%5C%5Ek%29%29)
⇒ ![(\^i\frac{\partial}{\partial x}+\^j \frac{\partial}{\partial y}+\^k\frac{\partial}{\partial z})\times ((aM+bQ)\^i+(aN+bR)\^j+(aP+bS)\^k)](https://tex.z-dn.net/?f=%28%5C%5Ei%5Cfrac%7B%5Cpartial%7D%7B%5Cpartial%20x%7D%2B%5C%5Ej%20%5Cfrac%7B%5Cpartial%7D%7B%5Cpartial%20y%7D%2B%5C%5Ek%5Cfrac%7B%5Cpartial%7D%7B%5Cpartial%20z%7D%29%5Ctimes%20%28%28aM%2BbQ%29%5C%5Ei%2B%28aN%2BbR%29%5C%5Ej%2B%28aP%2BbS%29%5C%5Ek%29)
Applying the cross product,
...(3)
Consider R.H.S,
⇒ ![a\nabla\times F1+b\nabla\times F2](https://tex.z-dn.net/?f=a%5Cnabla%5Ctimes%20F1%2Bb%5Cnabla%5Ctimes%20F2)
So,
![a\nabla\times F1=a(\nabla\times (M\^i+N\^j+P\^k))](https://tex.z-dn.net/?f=a%5Cnabla%5Ctimes%20F1%3Da%28%5Cnabla%5Ctimes%20%28M%5C%5Ei%2BN%5C%5Ej%2BP%5C%5Ek%29%29)
⇒ ![\^i(\frac{\partial aP\^k}{\partial y}- \frac{\partial aN\^j}{\partial z})+\^j(\frac{\partial aM\^i}{\partial z}-\frac{\partial aP\^k}{\partial x})+\^k(\frac{\partial aN\^j}{\partial x}-\frac{\partial aM\^i}{\partial y})](https://tex.z-dn.net/?f=%5C%5Ei%28%5Cfrac%7B%5Cpartial%20aP%5C%5Ek%7D%7B%5Cpartial%20y%7D-%20%5Cfrac%7B%5Cpartial%20aN%5C%5Ej%7D%7B%5Cpartial%20z%7D%29%2B%5C%5Ej%28%5Cfrac%7B%5Cpartial%20aM%5C%5Ei%7D%7B%5Cpartial%20z%7D-%5Cfrac%7B%5Cpartial%20aP%5C%5Ek%7D%7B%5Cpartial%20x%7D%29%2B%5C%5Ek%28%5Cfrac%7B%5Cpartial%20aN%5C%5Ej%7D%7B%5Cpartial%20x%7D-%5Cfrac%7B%5Cpartial%20aM%5C%5Ei%7D%7B%5Cpartial%20y%7D%29)
![a\nabla\times F2=b(\nabla\times (Q\^i+R\^j+S\^k))](https://tex.z-dn.net/?f=a%5Cnabla%5Ctimes%20F2%3Db%28%5Cnabla%5Ctimes%20%28Q%5C%5Ei%2BR%5C%5Ej%2BS%5C%5Ek%29%29)
⇒ ![\^i(\frac{\partial bS\^k}{\partial y}- \frac{\partial bR\^j}{\partial z})+\^j(\frac{\partial bQ\^i}{\partial z}-\frac{\partial bS\^k}{\partial x})+\^k(\frac{\partial bR\^j}{\partial x}-\frac{\partial bQ\^i}{\partial y})](https://tex.z-dn.net/?f=%5C%5Ei%28%5Cfrac%7B%5Cpartial%20bS%5C%5Ek%7D%7B%5Cpartial%20y%7D-%20%5Cfrac%7B%5Cpartial%20bR%5C%5Ej%7D%7B%5Cpartial%20z%7D%29%2B%5C%5Ej%28%5Cfrac%7B%5Cpartial%20bQ%5C%5Ei%7D%7B%5Cpartial%20z%7D-%5Cfrac%7B%5Cpartial%20bS%5C%5Ek%7D%7B%5Cpartial%20x%7D%29%2B%5C%5Ek%28%5Cfrac%7B%5Cpartial%20bR%5C%5Ej%7D%7B%5Cpartial%20x%7D-%5Cfrac%7B%5Cpartial%20bQ%5C%5Ei%7D%7B%5Cpartial%20y%7D%29)
Then,
=
![\^i(\^k\frac{\partial (aP+bS)}{\partial y}- \^j\frac{\partial (aN+bR)}{\partial z})+\^j(\^i\frac{\partial (aM+bQ)}{\partial z}-\^k\frac{\partial (aP+bS)}{\partial x})+\^k(\^j\frac{\partial (aN+bR)}{\partial x}-\^i\frac{\partial (aM+bQ)}{\partial y})](https://tex.z-dn.net/?f=%5C%5Ei%28%5C%5Ek%5Cfrac%7B%5Cpartial%20%28aP%2BbS%29%7D%7B%5Cpartial%20y%7D-%20%5C%5Ej%5Cfrac%7B%5Cpartial%20%28aN%2BbR%29%7D%7B%5Cpartial%20z%7D%29%2B%5C%5Ej%28%5C%5Ei%5Cfrac%7B%5Cpartial%20%28aM%2BbQ%29%7D%7B%5Cpartial%20z%7D-%5C%5Ek%5Cfrac%7B%5Cpartial%20%28aP%2BbS%29%7D%7B%5Cpartial%20x%7D%29%2B%5C%5Ek%28%5C%5Ej%5Cfrac%7B%5Cpartial%20%28aN%2BbR%29%7D%7B%5Cpartial%20x%7D-%5C%5Ei%5Cfrac%7B%5Cpartial%20%28aM%2BbQ%29%7D%7B%5Cpartial%20y%7D%29)
...(4)
Thus, from (3) and (4),
![\nabla\times(aF1+bF2)=a\nabla\times F1+b\nabla\times F2](https://tex.z-dn.net/?f=%5Cnabla%5Ctimes%28aF1%2BbF2%29%3Da%5Cnabla%5Ctimes%20F1%2Bb%5Cnabla%5Ctimes%20F2)
Learn more about divergence and curl of a vector field here:
brainly.com/question/4608972
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Disclaimer: The given question on the portal is incomplete.
Question: Let
and
be differential vector fields and let a and b arbitrary real constants. Verify the following identities.
![1)\nabla.(aF1+bF2)=a\nabla.F1+b\nabla.F2\\2)\nabla\times(aF1+bF2)=a\nabla\times F1+b\nabla\times F2](https://tex.z-dn.net/?f=1%29%5Cnabla.%28aF1%2BbF2%29%3Da%5Cnabla.F1%2Bb%5Cnabla.F2%5C%5C2%29%5Cnabla%5Ctimes%28aF1%2BbF2%29%3Da%5Cnabla%5Ctimes%20F1%2Bb%5Cnabla%5Ctimes%20F2)