Get me into Oxford - Trig problem

[Rolen]

A pendulum is swinging through an angle of 80 degrees. The angle X (degrees), between the pendulum and the vertical, at time T, is given by X=a.Cos(60+T degrees).

Find a and the period of the pendulum.

My solution for finding a,

X=40(deg) when T=0
40(deg)=a.Cos(0)
Cos(0)=1
a=40

For the next part i'm unsure of the value for X (160?), and even if I assume any value i've not been taught how to manipulate trig equasions in this form.

Thanks, Max.

[kbinder]

Is this problem part of an Oxford application?

For part b:
cos(a+b) = cos(a)cos(b) - sin(a)sin(b)

[MrMon]

I'm pretty sure this is a physics problem, not a trig problem and most of the info given is unnecessary to solve the period.

[pokergrader]

[ QUOTE ]
Is this problem part of an Oxford application?

For part b:
cos(a+b) = cos(a)cos(b) - sin(a)sin(b)

[/ QUOTE ]

Nah, you certainly dont need to use this to find the period.

[evank15]

[ QUOTE ]
A pendulum is swinging through an angle of 80 degrees. The angle X (degrees), between the pendulum and the vertical, at time T, is given by X=a.Cos(60+T degrees).

[/ QUOTE ]

That equation does not describe anything (that is to say it is nonsensical), do you see why?

[Rolen]

no

[CheckRaise]

Ok, I'm a little confused here, a general position equation for SHM is: X=Acos(omega*t + phi)
where A is the amplitude, omega is the angular frequency and phi is the phase angle, which I think we can ignore in this problem.

The equation you posted doesn't make sense, cos(60 + T degrees). What is T degrees and what does that 60 represent?

Someone correct me if I'm wrong because I'm certainly no expert on this matter but this is my take on the problem.

[Rolen]

No, sorry I see where the confustion is..(60+T) degrees where T is time in sec. I'm struggling with mathematical notation on the comp.

[evank15]

Hint: What's ten kilograms plus eight joules?

SHM: Acos(wt+p)

where w is the angular frequency, t the time and p is the phase angle.

Although really, a pendulum oscillating through 80 degrees does not exhibit simple harmonic motion, so the whole question is kind of [censored].

[evank15]

we need that latex support STAT!