Question

Could someone please explain to me how y2= cosx is found in this series solution problem?
y'' +y=0
y(0)=1, y'(0)=0
I understand how to find y1 b/c the odd terms stay, but how is cosx found because the even terms are zero?

Answer 1

Do you want me to use only series to solve it?

Answer 2

Yes

Answer 3

.

Answer 4

Sorry- I meant the other way around- cosx can be seen easily- but not sinx. Is the Maclaurin series just multiplied by x?

Answer 5

No, the factorial denominators are shifted too.