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I'm trying to solve a differential equation with DESOLVE, but I get bad argument type error message. Numeric, Approx and Complex CAS flags are disabled (actually I disabled all CAS flags).

Here is what I enter on RPN mode:
1. [ 'd1d1y(t)+5*y(t)=2*COS(t/2)' 'y(0)=6/5' 'd1y(0)=-1/2'] + ENTER
2. 'y(t)'
3. DESOLVE (LEFT SHIFT + 4[CALC] + F3[DIFF] + F1[DESOL])
Note: I'm using soft menus (flag 117 set).

Does anybody have any clue why I'm getting the error?

Hello dns.olic,

I keyed in:

1. 'd1d1y(t)=2*COS(t/2)-5*y(t)'
2. 'y(t)'

And use DESOLVE and I get a result with the two constants cC0 and cC1.

If I key in 'd1d1y(t)+5*y(t)=2*COS(t/2)' and not 'd1d1y(t)=2*COS(t/2)-5*y(t)', I although get an error message.

Same procedure with constrains, same behavior DESOLVE works with:
[ 'd1d1y(t)=2*COS(t/2)-5*y(t)' 'y(0)=6/5' 'd1y(0)=-1/2'] + ENTER
2. 'y(t)'

Hello,

it may be useful to read this tutorial:

Using Desolve
https://www.hpcalc.org/details/7291
https://www.hpcalc.org/hp49/docs/misc/usingdesolve.pdf


regards
Simone