Differentiation and applications

Second derivatives

(* Ignore this section* - wk 5, 5B Q 5,6,9,11 )

Please answer the questions on the attachment below. ( ON PAPER/WRITTEN ) ( Please keep solving and explanation seperate)

d2 5 If y = cos x, show that E - d.x2 - y . d2 6 If y = sin 3x, show that: y + 9y = 0. dx29 Find the value of k if y = e-kx and d'y = 25y . dx2