- #1
Blue Kangaroo
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Homework Statement
Take ∂2E/∂t2 E(r,t)=E0cos((k(u^·r−ct)+φ) in which u^ is a unit vector.
Homework Equations
d/dx(cosx)=-sinx
The Attempt at a Solution
I had calc 3 four years ago and can't for the life of me remember how to differentiate the unit vector. I came up with -c2u2^cos(k(u^r-ct)+φ), but I feel like I'm not doing that right.
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