If I have 2 experiments measuring the same thing. For example, I measure the voltage with 2 different tools (2 different voltmeters). I can calculate the final average in 2 different ways. For example, I have 7 measurements with the first tool and 5 measurements with the second tool for whatever ...

An electrodynamics lecture asks me to prove that $$ \nabla \times \left( \frac{\vec{M} \times \vec{x}}{ |\vec{x}|^3} \right) = \frac{8 \pi}{3} \vec{M} \delta^3(\vec{x})- \frac{\vec{M}}{|\vec{x}|^3}+ \frac{3\vec{M} \cdot \vec{x}}{|\vec{x}|^5}\vec{x} $$ where $\vec{M}$ is some constant vector. I ha...