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Function DESOLVE
The calculator provides function DESOLVE (Differential Equation SOLVEr) to solve certain types of differential equations. The function requires as input the differential equation and the unknown function, and returns the solution to the equation if available. You can also provide a vector containing the differential equation and the initial conditions, instead of only a differential equation, as input to DESOLVE. The function DESOLVE is available in the CALC/DIFF menu. Examples of DESOLVE applications are shown below using RPN mode.
Example 1 – Solve the
dy/dx + x2⋅y(x) = 5.
In the calculator use:
'd1y(x)+x^2*y(x)=5' `'y(x)' `DESOLVE
The solution provided is
{‘y(x) = (5*INT(EXP(xt^3/3),xt,x)+cC0)*1/EXP(x^3/3)}’ } , which simplifies to
y(x) = 5 ⋅ exp(−x3 / 3) ⋅ (∫ exp(x 3 / 3) ⋅ dx + C0 ).
The variable ODETYPE
You will notice in the
Example 2 – Solving an equation with initial conditions. Solve
d2y/dt2 + 5y = 2 cos(t/2),
with initial conditions
y(0) = 1.2, y’(0) =
In the calculator, use:
[‘d1d1y(t)+5*y(t) = 2*COS(t/2)’ ‘y(0) = 6/5’ ‘d1y(0) =
‘y(t)’ `
DESOLVE
Notice that the initial conditions were changed to their Exact expressions, ‘y(0) = 6/5’, rather than ‘y(0)=1.2’, and ‘d1y(0) =
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