In: Advanced Math
(9) (a) If f(t) = x1e −kt cos(ωt) + x2e −kt sin(ωt), then f'(t) has the same form with coefficients y1, y2.
(i) Find the matrix A such that y = Ax.
(ii) Find the characteristic polynomial of A.
(iii) What can you say about eigenvalues of A? (iv) Interpret your answer to
(iii) as a calculus statement. That is, explain how your answer to (iii) could have been predicted from a basic fact of calculus.
(b) If f(t) = x1 sin(t) + x2 cos(t) + x3tsin(t) + x4t cos(t), then f'(t) has the same form with coefficients y1, ..., y4. Same questions (a)-(d) as previously.