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Engineering Mathematics Miscellaneous

Engineering Mathematics

  1. The eigen values of a symmetric matrix are all
    1. complex with non-zero positive imaginary part
    2. complex with non-zero negative imaginary part
    3. real
    4. pure imaginary
Correct Option: C

Suppose the eigen value of matrix A is n
(= λ + i BB) say.
and the eigen vector is n whereas the conjugate pair of eigen value and eigen vector is λ and n
So, An = λ n ...(1)
And An = λ n ...(2)
Taking transpose of equation
x-TAT = x-Tλ ...(3)
⇒ x-TAT = x-T⇒ x-TAn = x-T⇒ λ = λ
⇒ α + iβ = α - iβ
⇒ 2iβ = 0
⇒ β = 0
Hence eigen value of a symmetric matrix are real



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