# 2- and 3-Body Demo

Two and three body problems.

```function f2body (x,y,m1,m2)

y=f(x,y) for the differential equations
```
```function test2body (y1,m1=1,m2=1,n=100,tmax=360,fixed=0,h=1)

2-body demo

Intial y is a row vector with two positions and two speed vectors
in the form [x1,y1,x2,y2,vx1,vy1,vx2,vy2]. m1 and m2 are the masses
of the two bodies.

For slower animation increase h. For more accuracy increase n. The
simulation runs until one body leaves the definition area (unless
fixed is true), or tmax is reached.

>fixed fixes the display at the first mass, which is positioned
in (0,0).
```

## Functions

```function f3body (x,y,m1,m2,m3)

y=f(x,y) for the differential equations
```
```function test3body (y1,m1=1,m2=1,m3=1,n=100,fixed=0,tmax=360,h=1)

3-body demo

Works like test2body, but takes three positions and speed vectors,
and three masses.
```

## Set Planets

```function setplanets

Set the planets and initial vectors with the mouse.

3-body which sets the positions with the mouse.
```

Examples