# Math Help - Trig Modelling

1. ## Trig Modelling

A mass on a spring moves up and down with its displacement given by;
x=3-4cos((2pi/5)t). X is in centimetres and t is in seconds.

a)find the inital displacement
b)the displacement after 30 seconds
c)the greatest displacement

Help greatly appreciated in advance

2. Hi
Originally Posted by Webby
A mass on a spring moves up and down with its displacement given by;
x=3-4cos((2pi/5)t). X is in centimetres and t is in seconds.

a)find the inital displacement
This is $x(0)=3-4\cos\left(\frac{2\pi}{5}\cdot 0\right)= ?$
b)the displacement after 30 seconds
This is $x(30)=3-4\cos\left(\frac{2\pi}{5}\cdot 30\right)= ?$
c)the greatest displacement
Find the maximum of $x(t)$ using its derivative or the properties of the cosine function.