An oblique basis has

PHYSICS · Multi-part · Fermi University Physics · Mathematical Methods for Physics · Tensors and differential geometry · Tensors and differential geometry

Invariance, Ch General bases, the metric and tensors in spacetime

Problem

An oblique basis has ∣e1∣=3.0 A˚|\mathbf{e}_1| = 3.0\,\text{\AA}, ∣e2∣=4.0 A˚|\mathbf{e}_2| = 4.0\,\text{\AA} and an angle of 75∘75^\circ between them, so that g11=9.0 A˚2g_{11} = 9.0\,\text{\AA}^2, g22=16.0 A˚2g_{22} = 16.0\,\text{\AA}^2 and g12=g21=∣e1∣∣e2∣cos⁡75∘g_{12} = g_{21} = |\mathbf{e}_1||\mathbf{e}_2|\cos75^\circ. A vector has (dimensionless) contravariant components Vi=(2,1)V^i = (2, 1). ((a)) Find the covariant components Vi=gijVjV_i = g_{ij}V^j. ((b)) Find the length ∣V∣=ViVi|\mathbf{V}| = \sqrt{V^iV_i}.

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