I'm having trouble using the equations for SHM calculations. We got told to set them on radians but I forgot to when I was doing the problems and got some of the answers right. But when I tried to do them when the calculator was set in radians, the answers were totally wrong.

We are given a set of equations to use

x=Xcos(2πft)

v= -X√(k/m)sin(2πft)

a= -XK/mcos(2πft)

Do we set the calculator to radians when we use these equations?

Do we take into account the negative "-" sign in front of X for the velocity and acceleration equations?

I'll show you the working a question I did and maybe you can see where I went wrong.

**1. The problem statement, all variables and given/known data**

A 64kg bungy jumper is displaced 13m from equilibrium downwards and then released. She bounces up and down with a period of 5.4s. When she is 5m abover her initial rest position and moving upwards, what is her velocity?

**2. The attempt at a solution**

I calculated this with my calculator set in degrees

x=Xcos(2πft)

5=13cos(2π x 1/5.4t)

t= 57.9s

v= -X√(k/m)sin(2πft)

v= -13√(86.6/64)sin(2π x 1/5.4 x 57.9)

v= -14m/s

The answer was 14m/s. Why was the negative sign ignored?

But when we were asked to calculate the acceleration at 5m displacement the answer is

-6.77m/s

^{2}

a= -XK/mcos(2πft)

a= -13 x 86.6/64cos(2π x 1/5.4 x 57.9)

a= -6.77m/s

^{2}

**Calculator still set in degrees**

If anyone could help that would be very appreciated. Thanks