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Let A=({:(cosalpha,-,sinalpha),(sinalpha...

Let `A=({:(cosalpha,-,sinalpha),(sinalpha,,cosalpha):}),(alphaepsilonR)` such that
`A^(32)=({:(0,-1),(1,0):})`. Then a value of `alpha` is:

A

0

B

`pi/16`

C

`pi/32`

D

`pi/64`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem step by step, we need to find the value of \( \alpha \) such that the matrix \( A^{32} = \begin{pmatrix} 0 & -1 \\ 1 & 0 \end{pmatrix} \). ### Step 1: Define the matrix \( A \) The matrix \( A \) is given as: \[ A = \begin{pmatrix} \cos \alpha & -\sin \alpha \\ \sin \alpha & \cos \alpha \end{pmatrix} \] ### Step 2: Calculate \( A^2 \) To find \( A^{32} \), we first need to calculate \( A^2 \): \[ A^2 = A \cdot A = \begin{pmatrix} \cos \alpha & -\sin \alpha \\ \sin \alpha & \cos \alpha \end{pmatrix} \cdot \begin{pmatrix} \cos \alpha & -\sin \alpha \\ \sin \alpha & \cos \alpha \end{pmatrix} \] Using matrix multiplication: - The (1,1) entry: \( \cos^2 \alpha + \sin^2 \alpha = 1 \) - The (1,2) entry: \( -\cos \alpha \sin \alpha + \sin \alpha \cos \alpha = 0 \) - The (2,1) entry: \( \sin \alpha \cos \alpha + \cos \alpha \sin \alpha = 0 \) - The (2,2) entry: \( \sin^2 \alpha + \cos^2 \alpha = 1 \) Thus, \[ A^2 = \begin{pmatrix} \cos 2\alpha & -\sin 2\alpha \\ \sin 2\alpha & \cos 2\alpha \end{pmatrix} \] ### Step 3: Generalize \( A^n \) From the pattern observed, we can generalize: \[ A^n = \begin{pmatrix} \cos n\alpha & -\sin n\alpha \\ \sin n\alpha & \cos n\alpha \end{pmatrix} \] ### Step 4: Calculate \( A^{32} \) Using the general formula: \[ A^{32} = \begin{pmatrix} \cos 32\alpha & -\sin 32\alpha \\ \sin 32\alpha & \cos 32\alpha \end{pmatrix} \] We know that: \[ A^{32} = \begin{pmatrix} 0 & -1 \\ 1 & 0 \end{pmatrix} \] ### Step 5: Set up equations From the equality of matrices, we have: 1. \( \cos 32\alpha = 0 \) 2. \( -\sin 32\alpha = -1 \) or \( \sin 32\alpha = 1 \) ### Step 6: Solve \( \cos 32\alpha = 0 \) The cosine function is zero at: \[ 32\alpha = \frac{\pi}{2} + k\pi \quad (k \in \mathbb{Z}) \] This gives: \[ \alpha = \frac{\pi}{64} + \frac{k\pi}{32} \] ### Step 7: Solve \( \sin 32\alpha = 1 \) The sine function equals 1 at: \[ 32\alpha = \frac{\pi}{2} + 2m\pi \quad (m \in \mathbb{Z}) \] This also gives: \[ \alpha = \frac{\pi}{64} + \frac{m\pi}{16} \] ### Step 8: Find a specific solution The simplest solution occurs when \( k = 0 \) and \( m = 0 \): \[ \alpha = \frac{\pi}{64} \] Thus, the value of \( \alpha \) is: \[ \boxed{\frac{\pi}{64}} \]

To solve the problem step by step, we need to find the value of \( \alpha \) such that the matrix \( A^{32} = \begin{pmatrix} 0 & -1 \\ 1 & 0 \end{pmatrix} \). ### Step 1: Define the matrix \( A \) The matrix \( A \) is given as: \[ A = \begin{pmatrix} \cos \alpha & -\sin \alpha \\ \sin \alpha & \cos \alpha \end{pmatrix} \] ...
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