Explain why or why not Determine whether the following statements are true and
give an explanation or counterexample.
a. \(\operatorname{proj}_{\mathbf{v}}
\mathbf{u}=\operatorname{proj}_{\mathbf{u}} \mathbf{v}\)
b. If nonzero vectors \(\mathbf{u}\) and \(\mathbf{v}\) have the same magnitude,
they make equal angles with \(\mathbf{u}+\mathbf{v}\)
c. \((\mathbf{u} \cdot \mathbf{i})^{2}+(\mathbf{u} \cdot
\mathbf{j})^{2}+(\mathbf{u} \cdot \mathbf{k})^{2}=|\mathbf{u}|^{2}\)
d. If \(\mathbf{u}\) is orthogonal to \(\mathbf{v}\) and \(\mathbf{v}\) is
orthogonal to \(\mathbf{w},\) then \(\mathbf{u}\) is orthogonal to \(\mathbf{w}\)
e. The vectors orthogonal to\( \langle 1,1,1\rangle\) lie on the same line.
f. If proju \(\mathbf{u}=\mathbf{0},\) then vectors \(\mathbf{u}\) and
\(\mathbf{v}\) (both nonzero) are orthogonal.