Explanation on how these solutions can be easily seen

[mazz1801]

Explanation on how these solutions can be "easily" seen

Homework Statement

Show that x₁(t)=cos(t) and x₂(t)=sin(t) are both solutions to the following Equation.

Homework Equations

(d²x/dt²) + x = 0

The Attempt at a Solution

Ok, So I just cannot understand how this can easily be seen! I cannot see it at all!
I know I haven't got any work to show you and that is wrong but I honestly do not know where to start with this.

It is in the middle of some lecture notes and all they say is "this can easily be seen"

Please Help this dummy!:'(

 

[Dick]

Find the second derivatives of sin(t) and cos(t). Once you do that it should be 'easily seen'.

 

[mazz1801]

Gosh now I feel super dumb :P Thanks a million!