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For some a, b, let f(x)=beginvmatrix a+fracsin xx & 1 & b \\ a & 1+fracsin xx & b \\ a & 1 & b+fracsin xx endvmatrix, xne0 [cite: 3370, 3371, 3372, 3374, 3375] lim_xrightarrow0f(x)=lambda+mu a+vb [cite: 3376, 3377] Then (lambda+mu+nu)^2 is equal to:

Solution & Explanation

### Related Formula The fundamental trigonometric limit is given by: lim_x to 0 fracsin xx = 1 ### Core Logic Apply the limit inside each element of the matrix determinant : lim_x to 0 f(x) = beginvmatrix a+1 & 1 & b \\ a & 2 & b \\ a & 1 & b+1 endvmatrix ### Step 1: Simplify the Determinant via Row Operations Perform rows reductions R_2 to R_2 - R_1 and R_3 to R_3 - R_1 to create zeros: lim_x to 0 f(x) = beginvmatrix a+1 & 1 & b \\ -1 & 1 & 0 \\ -1 & 0 & 1 endvmatrix Expand across the first row : = (a+1)[1(1) - 0] - 1[-1(1) - 0] + b[0 - (-1)] = (a+1)(1) + 1 + b = a + b + 2 [cite: 3999, 4000] ### Step 2: Match Coefficients Equate this outcome with the target parameter template lambda + mu a + nu b [cite: 3377, 4000]: lambda = 2, quad mu = 1, quad nu = 1 Calculate (lambda + mu + nu)^2 [cite: 3378, 4001]: (2 + 1 + 1)^2 = 4^2 = 16 ### Pattern Recognition Standard row manipulations on identity-shifted arrays quickly eliminate complex parameter symbols, reducing determinant calculations into straightforward polynomial expansions. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Mathematics: Matrices and Determinants Class 11 Mathematics: Limits and Derivatives

Reference Study Guides

More Matrices and Determinants Previous-Year Questions — Page 6

Q70 2025 Cofactors and Determinant Value
Let mathrmA = left[mathbfa_mathrmijright] = beginbmatrix log_5128 & log_45 \\ log_58 & log_425 endbmatrix . If A_ij is the cofactor of a_ij , C_ij = sum_k=1^2 a_ik A_jk , 1 leq i, j leq 2 , and C = [C_ij] , then 8|C| is equal to:
  • A. 262
  • B. 288
  • C. 242
  • D. 222

Solution

### Related Formula sum_k a_ik A_jk = delta_ij |A| implies C = beginbmatrix |A| & 0 \\ 0 & |A| endbmatrix implies |C| = |A|^2 ### Core Logic Evaluate the determinant of matrix A: |A| = (log_5 128)(log_4 25) - (log_4 5)(log_5 8) Using change of base rules: |A| = left(7log_5 2right)left(2log_4 5right) - left(frac12log_2 5right)left(3log_5 2right) |A| = 14left(log_5 2 cdot frac12log_2 5right) - frac32 = 7 - 1.5 = 5.5 = frac112 ### Step 1: Compute |C| and evaluate response target Since matrix properties dictate |C| = |A|^2: |C| = left(frac112right)^2 = frac1214 Evaluate targeted multiplier: 8|C| = 8 times frac1214 = 2 times 121 = 242 ### Pattern Recognition Recognize the core cofactor theorem identity instantly: multiplying rows by cofactors of other rows creates zero elements, yielding basic diagonal scalar structures matching matrix attributes. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Mathematics: Matrices and Determinants

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