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Unformatted text preview: Exponential of 2 × 2 Matrices These notes describe how to calculate e tA for a 2 × 2 matrix A . We recall that by definition the exponential of a matrix is e tA = ∞ X n =0 t n A n n ! . For computations the basic relation we will use is e tP 1 AP = P 1 e tA P ⇒ e tA = Pe tP 1 AP P 1 . There are three cases to consider: 1. A has real eigenvalues and is diagonalizable. 2. A has real eigenvalues but is not diagonalizable. 3. A has a pair of complex conjugate eigenvalues. Case 1: real eigenvalues & diagonalizable This case comes down to calculating the exponential of a diagonal matrix. Let B be the matrix B = λ 1 t λ 2 t . It is easy to verify that B n = λ n 1 t n λ n 2 t n . Therefore e B = ∞ X n =0 B n n ! = ∑ ∞ n =0 λ n 1 t n n ! ∑ ∞ n =0 λ n 2 t n n ! = e λ 1 t e λ 2 t . Returning to A , let λ 1 and λ 2 be its eigenvalues (note that λ 1 and λ 2 need not be distinct). In this case we can find two independent eigenvectorsdistinct)....
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This note was uploaded on 05/24/2011 for the course MAT 244 taught by Professor Christinasaleh during the Spring '10 term at University of Toronto.
 Spring '10
 ChristinaSaleh
 Matrices

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