Simple Harmonic Motion (1 Viewer)

[j1mmy_]

I need help with part ii)

This is from last year's HSC paper by the way.

So putting when displacement is 0, x = 0

5 + 6cos2t + 8sin2t = 0
6cos2t + 8sin2t = -5

Stuck here. Had a look at the solutions but I'm lost.

 

[nightweaver066]

Auxiliary angle method to solve it.

 

[j1mmy_]

Auxiliary angle method to solve it.

Oh right, thanks!