Let V = W = R2. Choose the basis B = {x1, x2} of V , where x1 = (2, 3), x2 = (4,−5) and choose the basis D = {y1,y2} of W, where y1 = (1,1), y2 = (−3,4). Find the matrix of the identity linear mapping I : V → W with respect to these bases.
Let A =
1 |
-3 |
2 |
4 |
1 |
4 |
3 |
-5 |
The RREF of A is
1 |
0 |
17/7 |
1/7 |
0 |
1 |
1/7 |
-9/7 |
Hence (2,3) = (17/7)(1,1)+(1/7)(-3,4) and (4,-5) = (1/7)(1,1)-(9/7)(-3,4).
Let I: V →W be the identity linear mapping. Then I( x1) = I(2,3) = (2,3) = (17/7)(1,1)+(1/7)(-3,4) and I ( x2) = I(4,-5) = (4,-5)= (1/7)(1,1)-(9/7)(-3,4).
Thus, the matrix of the identity linear mapping I : V →W with respect to the bases B and D is M =
17/7 |
1/7 |
1/7 |
-9/7 |
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