Question $7(6$ points$)$

Consider the differential equation

$y^{\text{'}\text{'}}+9y=cos(t)$

Select all true statements.

When $=9\mathrm{.}01,$ the solution will exhibit beats.

When $=3\mathrm{.}01,$ the solution will exhibit beats.

When $=9,$ the solution will exhibit resonance.

Resonance is not possible in this case, since there is no friction.

Resonance happens when the driving frequency equals the natural frequency, in the absence of friction.

When $=2\mathrm{.}99,$ the solution will exhibit beats.

When $=3,$ the solution will exhibit beats.

Beats happens when the driving frequency equals the natural frequency, in the