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Homework Statement:

if Φ=Φ(λx,λy,λz) = λ^n(x,y,z)
proof that r.grad(Φ) = nΦ
Relevant Equations:

Φ=Φ(λx,λy,λz) = λ^n(x,y,z)
r.grad(Φ) = nΦ
hi guys i saw this problem in my collage textbook on vector calculus , i don't know if the statement is wrong because it don't make sense to me
so if any one can help on getting a hint where to start i will appreciate it , basically it says :
$$ \phi =\phi(\lambda x,\lambda y,\lambda z)=\lambda^{n}(x,y,z) $$
prove that
$$\vec{r} . \vec{\nabla}\phi=n\phi$$
so if any one can help on getting a hint where to start i will appreciate it , basically it says :
$$ \phi =\phi(\lambda x,\lambda y,\lambda z)=\lambda^{n}(x,y,z) $$
prove that
$$\vec{r} . \vec{\nabla}\phi=n\phi$$