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Class 12 Matrices · Assertion Reason1 Marksassertion_reason

Class 12 Maths · Matrices · Assertion Reason #29

Assertion: If A=\(\begin{bmatrix}\cos\theta & \sin\theta\\-\sin\theta & \cos\theta\end{bmatrix}\), then A²=\(\begin{bmatrix}\cos2\theta & \sin2\theta\\-\sin2\theta & \cos2\theta\end{bmatrix}\). Reason: For this rotation matrix and every positive integer n, Aⁿ=\(\begin{bmatrix}\cos n\theta & \sin n\theta\\-\sin n\theta & \cos n\theta\end{bmatrix}\).

✅ Step-by-Step Solution

Final Answer: Option (A): Both A and R are true, and R correctly explains A.
  1. The rotation addition formulas give A(α)A(β)=A(α+β); induction gives the stated power formula, and n=2 gives the assertion.

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