ABSTRACT
Instead of considering the transformation properties of irreducible tensors under finite rotations, we will now consider transformations under infinitesimal rotations. Those rotations can be characterized by choosing a definite axis and a rotation around it by an infinitesimal angle δϕ. Consider rotations around the z-axis (z′ = z). Under a finite anticlockwise rotation of the frame of reference by an angle ϕ, the coordinates x′, y′ are given in terms of x, y by () x ′ = x cos ϕ + y sin ϕ x = x ′ cos ϕ − y ′ sin ϕ y ′ = − x sin ϕ + y cos ϕ y = x ′ sin ϕ + y ′ cos ϕ https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780203739716/ff034a11-a369-4bc6-a470-f8cf1794dcb5/content/eq268.tif"/>
