Vector Calculus: Is F=0 When ∇·F=0 & ∇×F=0?

latentcorpse
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is it true that if \nabla \cdot \vec{F}=0 , \nabla \times \vec{F}=0 then \vec{F}=0?
 
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latentcorpse said:
is it true that if \nabla \cdot \vec{F}=0 , \nabla \times \vec{F}=0 then \vec{F}=0?

Suppose \vec F=3\hat x \ldots
 
the divergence of 3x is 3 not 0 though?
 
latentcorpse said:
the divergence of 3x is 3 not 0 though?

By \hat x, I mean what you might have seen as \hat \imath...
that is,
\vec F= (3) \hat \imath
or
\vec F= (3,0,0)
...that is, a nonzero constant vector field.
 
Prove $$\int\limits_0^{\sqrt2/4}\frac{1}{\sqrt{x-x^2}}\arcsin\sqrt{\frac{(x-1)\left(x-1+x\sqrt{9-16x}\right)}{1-2x}} \, \mathrm dx = \frac{\pi^2}{8}.$$ Let $$I = \int\limits_0^{\sqrt 2 / 4}\frac{1}{\sqrt{x-x^2}}\arcsin\sqrt{\frac{(x-1)\left(x-1+x\sqrt{9-16x}\right)}{1-2x}} \, \mathrm dx. \tag{1}$$ The representation integral of ##\arcsin## is $$\arcsin u = \int\limits_{0}^{1} \frac{\mathrm dt}{\sqrt{1-t^2}}, \qquad 0 \leqslant u \leqslant 1.$$ Plugging identity above into ##(1)## with ##u...
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