Lakshya JEE 2025 Maths DPP: 1 - Determinants
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Questions and Answers

What is the value of the determinant given by the expression ∣sin(A + B + C) sin B cos C∣?

  • 2 sin A sin B ⋅ sin C
  • 1
  • 2 sin B ⋅ tan A cos C
  • 0 (correct)
  • If A + B + C = π, what is the simplification of the expression sin(A + B + C)?

  • sin(A + B)
  • 0 (correct)
  • sin(C)
  • 1
  • Given the determinant setup, what does it imply about the relationship among a, b, and c if it equals zero?

  • a, b, c are in G.P.
  • a, b, c are independent.
  • a, b, c are equal.
  • a, b, c are in A.P. (correct)
  • What does the cofactor of the element 4 in a 3x3 determinant represent?

    <p>The determinant of a 2x2 matrix formed by removing the row and column of 4.</p> Signup and view all the answers

    In the expression involving determinant with values a, b, c, if it equals zero, what can be inferred?

    <p>Values are linearly dependent.</p> Signup and view all the answers

    What conditions must be met for the expression ∣a b aα + b∣ to yield a consistent equation?

    <p>α must be a real number.</p> Signup and view all the answers

    If the equation involving determinants holds for some values of a, b, and c, what kind of relationship is indicative of its solution?

    <p>It indicates a linear relationship.</p> Signup and view all the answers

    What is a possible interpretation of the condition ∣b α + c 0∣ = 0 in a determinant?

    <p>It indicates a proportional relationship between b and c.</p> Signup and view all the answers

    What is the determinant of the matrix formed by $\begin{vmatrix} a2 & b2 & c2 \ b2 & c3 & -b3 c2 \ a3 & c2 & a2 c3 \ \end{vmatrix}$ when $a2 b2 c2 = 5$?

    <p>1</p> Signup and view all the answers

    If the value of the third order determinant is 11, what is the value of the square of the determinant formed by the cofactors?

    <p>121</p> Signup and view all the answers

    Which of the following expressions is equivalent to $\begin{vmatrix} cos(\alpha + \beta) & -sin(\alpha + \beta) & cos(2\beta) \end{vmatrix}$?

    <p>cos(α+β)</p> Signup and view all the answers

    For which values of $α$ is the determinant $D$ independent?

    <p>Both $α$ and $β$</p> Signup and view all the answers

    Using the values of $a2$, $b2$, and $c2$, which combination produces a determinant that evaluates to 5?

    <p>$\begin{vmatrix} a2 &amp; b3 &amp; c3 \ b2 &amp; c1 &amp; a1 \ 1 &amp; 1 &amp; 1 \ \end{vmatrix}$</p> Signup and view all the answers

    What is the outcome when calculating a determinant where two rows are identical?

    <p>Always zero</p> Signup and view all the answers

    Which configuration does NOT affect the determinant's value when performing row operations?

    <p>Adding a row multiplied by 0</p> Signup and view all the answers

    In terms of matrix dimensions, which option correctly explains the condition for a determinant to exist?

    <p>It must be a square matrix.</p> Signup and view all the answers

    What is the value of the determinant represented by the matrix ∣ 1 log b a ∣ ∣ log a b 1 ∣ ?

    <p>log b a</p> Signup and view all the answers

    If f(x) = ax^2 + ax - 1, what is the expression for f(2x) - f(x)?

    <p>ax(2a + 3x)</p> Signup and view all the answers

    What is the value of the determinant represented by the matrix ∣ 1 1 1 1 ∣ ∣ 1 2 3 4 ∣ ∣ 1 3 6 10 ∣ ?

    <p>0</p> Signup and view all the answers

    For the determinant ∣ a -1 0 ∣ ∣ ax 2 ∣ ∣ ax a ∣, what happens when 'a' is equal to zero?

    <p>The determinant equals 0</p> Signup and view all the answers

    If log_a(b) equals x, what does log_b(a) equal in terms of x?

    <p>1/x</p> Signup and view all the answers

    What will be the result of the determinant formed by ∣ 1 1 2 3 ∣ or ∣ 3 2 1 1 ∣?

    <p>Determinant equals 0</p> Signup and view all the answers

    Which property of determinants is demonstrated when a row of the matrix is multiplied by a scalar?

    <p>The determinant is multiplied by the scalar</p> Signup and view all the answers

    Which of the following statements about the multiplication of determinants is true?

    <p>The determinant of the product of two matrices equals the product of their determinants</p> Signup and view all the answers

    Study Notes

    Determinants Overview

    • A determinant is a scalar value that provides important information about a matrix, including whether it is invertible and the volume scaling factor of linear transformations.

    Evaluating Determinants

    • For the determinant:
      • [ \begin{vmatrix} 1 & \log_b a \ \log_a b & 1 \end{vmatrix} ]
      • The value can be expressed by options, with (B) log a b and (C) log b a being significant.

    Determinant Properties

    • A determinant can equal zero if the rows or columns are linearly dependent.
    • Example determinant:
      • [ \begin{vmatrix} 1 & 1 & 1 & 1 \ 1 & 2 & 3 & 4 \ 1 & 3 & 6 & 10 \ 1 & 4 & 10 & 20 \end{vmatrix} ]
      • The value of this determinant is assessed by given options, indicating properties of higher-order determinants.

    Cofactor Matrix

    • A cofactor refers to a minor matrix's determinant multiplied by (-1) raised to the sum of the indices of the element.
    • A third-order determinant's properties can indicate square values when cofactors are involved.

    Special Cases of Determinants

    • If ( A + B + C = \pi ), the specific determinant calculation leads to notable results, with options indicating various relationships based on trigonometric identities.

    Linear Relationships

    • Given the determinant equation:
      • [ \begin{vmatrix} a & b & a\alpha + b \ b & c & b\alpha + c \ a\alpha + b & b\alpha + c & 0 \end{vmatrix} = 0 ]
      • This suggests that ( a, b, c ) are in arithmetic progression (A.P.).

    Key Determinant Outcomes

    • Determinants provide solutions and contextual relationships in abstract algebra, linear algebra, and applications within calculus and differential equations.
    • Understanding the conditions under which determinants equal zero or specific values help solve complex equations efficiently.

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    Description

    Test your knowledge on determinants with this DPP for JEE. This quiz covers key concepts and problem-solving techniques essential for the Maths section of the Lakshya JEE 2025 preparation. Challenge yourself with various types of determinant problems to enhance your understanding and performance.

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