Problem

Let

A = BB^T + CC^T

, where

B = \begin{bmatrix} \cos \theta \\ \sin \theta \end{bmatrix}

C = \begin{bmatrix} \sin \theta \\ -\cos \theta \end{bmatrix}

;

\theta \in R

. Then

A

is : (a)

\begin{bmatrix} 0 & 0 \\ 0 & 0 \end{bmatrix}

(b)

\begin{bmatrix} 0 & 1 \\ 1 & 0 \end{bmatrix}

(c)

\begin{bmatrix} 1 & 0 \\ 0 & 1 \end{bmatrix}

(d)

\begin{bmatrix} 0 & 0 \\ 0 & 1 \end{bmatrix}