8 Elementary Differential Equations Section 46 Linear Models

8 Elementary Differential Equations Section 4.6 Linear Models: IVPs amples A mass weighing 2 pounds stretches a spring 6 inches. At t-0, the mass is released from a point 8i velocity of ift/s. Determine the equation of motion y(t). Express the equation of motion and the alternative form ()-A sinGot +0). Determine the frequency, period, amplitude, and a. b. phase of the motion. 141

Solution

I see that you are just confused about why there is a \"pi\"
We know that angle is usually written in degree or in radian.
If you take radian value then
tan^-1(-4)=-1.32 radian

If you take degree value then
tan^-1(-4)=-75.96 degree

symbol for indicating angle in radian is pi

that\'s why there we write -1.32 pi. :)