Find an inner product such that the vectors (-1, 2)T and (1, 2)T form an orthonormal basis of R^2.
4.1.11. Prove that every orthonormal basis of R^2 under the standard dot product has the form u1 = (cos θ, sin θ) and u2 = (± -sin θ, cos θ) for some 0 ≤ θ < 2π and some choice of ± sign.