## Instructions

DEW1 draws the solution of differential equation of first order with initial values t0 and y0. The program also draws the direction field.

### Drawing (Initial values)

Solution is drawn with initial values t0 and y0. Values can be entered in the t= and y= text fields, then clicking the Draw-button will draw the corresponding solution. Or the initial conditions can be clicked on with the mouse.

### Equation

A differential equation may be selected from the pre-defined examples or may by defined by user. For example, the equation

y' - 3*y + 2*t = 0

is first solved for y':

y' = 3*y - 2*t,

then the right side of equation is given to the program:

3*y - 2*t.

### Changing the scale (Scale)

The scale can be adjusted by chancing the values of tmin, tmax, ymin and ymax and clicking the Change scale -button.

### Numerical method (General)

The solution may be plotted by using one of the following algoritms: adaptive Runge-Kutta, Euler, improved Euler, Runge-Kutta or Adams-Bashforth.

For non-adaptive methods the stepsize may be adjusted via the Stepsize -textfield.

### Clearing (General)

Clear -button clears everything that has been drawn.

### Equation parser

The equation parser recognizes the following mathematical operations, elementary functions and variables:

-Basic operations: +, -, *, /, and power ^.
-Trigonometrical functions: sin(), cos(), tan(), asin(), acos(), atan().
-Elementary functions: exp(), abs(), sqrt() and log().
-Other functions: abs(), sign().
-Brackets: ().
-Variables: t, y.
There must always be an operator between two operands. For example, 2t+3y must be given to the program in the form of 2*t+3*y.