Question

Let V be the space spanned by the two functions cos(t) and sin(t). Find the matrix A of the linear transformation T(f(t))=f′′(t)+3f′(t)+7f(t) from V into itself with respect to the basis {cos(t),sin(t)}.

Answer 1

Answer: The matrix A of the linear transformation T(f(t)) = f''(t) + 3f'(t) + 7f(t) from the space spanned by the functions cos(t) and sin(t) into itself with respect to the basis {cos(t), sin(t)} can be found by computing the images of the basis vectors under T and expressing those images as linear combinations of the basis vectors.

We have:

T(cos(t)) = -cos(t)'' - 3cos(t)' - 7cos(t) = -cos(t) - 3(-sin(t)) - 7cos(t) = -8cos(t) - 3sin(t)

T(sin(t)) = -sin(t)'' - 3sin(t)' - 7sin(t) = -sin(t) - 3cos(t) - 7sin(t) = -8sin(t) + 3cos(t)

So, with respect to the basis {cos(t), sin(t)}, the matrix A is:

A = [ -8, -3; 3, -8 ]

This is the matrix representation of the linear transformation T with respect to the basis {cos(t), sin(t)}.

Explanation: