Space fderiv of inner product wave eq space fderiv
ClassicalMechanics.space_fderiv_of_inner_product_wave_eq_space_fderiv
Plain-language statement
If f₀ is a function of (inner ℝ x s - c * t), the fderiv of its components with respect to spatial coordinates is equal to the corresponding component of the propagation direction s times time derivative.
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