Question-171091

Question Number 171091 by pablo1234523 last updated on 07/Jun/22

Commented by pablo1234523 last updated on 07/Jun/22

how is the red expression obtained

f^{2 n + 1} (θ x) = \cos (\frac{(2 n + 1) π}{2} + θ x) = \cos (n π + \frac{π}{2} + θ x)

= - \sin (n π + θ x) = {(- 1)}^{n} \sin (θ x)

but the book is showing f^{2 n + 1} (θ x) = {(- 1)}^{n + 1} \cos (θ x)

Commented by pablo1234523 last updated on 07/Jun/22

p l e a s e h e l p