Question

An oscillator has an amplitude of 3.2. At this instant the displacement of the oscillator is 1.4. What are the two possible phases of the oscillator at this instant?

so i used the equation x=A cos (omega(t) + phase zero)

which looks like
1.4=3.2 cos phase
.4375=cos phase
so than i take
cos^-1 of .4375 to get the phase..is this right?

Answer 1

That looks good.
Remmeber there will be two phases that have a positive cosine value.

Answer 2

how do i figure that out?

Answer 3

arccos(0.4375)=+-1.118 radians.

cos(-1.118 radians) = cos( (2*pi) - 1.118 )
=cos(5.1652 radians)

either of these will give a cosine value of +0.4375