The differential equation system is given as follows:
ODE 1: y_{1}′ = f(x, y_{1}, y_{2})
ODE 2: y_{2}′ = g(x, y_{1}, y_{2})
The solution of the differential equations is calculated numerically. The used method can be selected. Three Runge-Kutta methods are available: Heun, Euler and Runge-Kutta 4.Order. The initial values y_{01} and y_{02} can be varied with the sliders on the vertical axis at x_{0} in the first chart. The value for x_{0} can be set in the numeric input field. In the input fields for the functions f(x, y_{1}, y_{2}) and g(x, y_{1}, y_{2}), up to three parameters a, b and c can be used and changed by the sliders in the graph. The number of grid vectors in state-space diagram can be set in the numeric field for the grid points. In the state-space diagram is plotted y_{2} on the vertical axis and y_{1} about the horizontal axis.
Grap the start point to move the initial values. Move the slider to see the grid at the given x value (time).
y_{1}′ = f(x, y_{1}, y_{2}) =
y_{2}′ = g(x, y_{1}, y_{2}) =
The general ODE second order is:
y′′ = f(x, y, y′)
With a substitution the differential equation of second order can be transformed to a differential system of first order.
Substitution:
y_{1} = y
y_{2} = y′
So the resulting ODE system of 1.order is:
y_{1}′ = y_{2}
y_{2}′ = f(x, y_{1}, y_{2})
Constants
Name | Description |
---|---|
LN2 | Natural logarithm of 2 |
LN10 | Natural logarithm of 10 |
LOG2E | Base 2 logarithm of EULER |
LOG10E | Base 10 logarithm of EULER |
PI | Ratio of the circumference of a circle to its diameter |
SQRT1_2 | Square root of 1/2 |
SQRT2 | Square root of 2 |
Trigonometric Functions
Function | Description |
---|---|
sin(x) | sine of x |
cos(x) | Cosine of x |
tan(x) | Tangent of x |
asin(x) | arcsine |
acos(x) | arccosine of x |
atan(x) | arctangent of x |
atan2(y, x) | Returns the arctangent of the quotient of its arguments. |
cosh(x) | Hyperbolic cosine of x |
sinh(x) | Hyperbolic sine of x |
Logarithm and Exponential
Function | Description |
---|---|
pow(b, e) | e to the b |
sqrt(x) | Square root of x |
exp(x) | EULER to the x |
log(x), ln(x) | Natural logarithm |
log(x, b) | Logarithm to base b |
log2(x), lb(x) | Logarithm to base 2 |
log10(x), ld(x) | Logarithm to base 10 |
More functions
Function | Description |
---|---|
ceil(x) | Get smallest integer n with n > x. |
abs(x) | Absolute value of x |
max(a, b, c, ...) | Maximum value of all given values. |
min(a, b, c, ...) | Minimum value of all given values. |
random(max = 1) | Generate a random number between 0 and max. |
round(v) | Returns the value of a number rounded to the nearest integer. |
floor(x) | Returns the biggest integer n with n < x. |
factorial(n) | Calculates n! |
trunc(v, p = 0) | Truncate v after the p-th decimal. |
V(s) | Returns the value of the given element, e.g. sliders and angles. |
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