Question: assign small angel assumptions

Hi,

I was wondering how I could assign small angel assumptions so that I could simplify an equation of motion to solve for theta double dot. Thank you for your help.


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Equation Manipulation

-assumptions- small angel

"sin(`ϑ`):=`ϑ`"

`ϑ`

(1)

"cos(`ϑ`):=1"

1

(2)

diff(`ϑ`(t), t) := 0

NULL

diff(x(t), t, t) := (H+u)/M


I*(diff(`ϑ`(t), t, t)) = [m*(-l*(diff(`ϑ`(t), t))^2*cos(`ϑ`)-l*(diff(`ϑ`(t), t, t))*sin(diff(`ϑ`(t), t)))-m*g]*l*sin(`ϑ`)+[m*(l*(diff(`ϑ`(t), t))^2*sin(`ϑ`)-l*(diff(`ϑ`(t), t, t))*cos(diff(`ϑ`(t), t))+diff(x(t), t, t))]*l*cos(`ϑ`)

"(->)"

Error, (in isolate) unable to isolate diff(diff(`ϑ`(t), t), t)

 

NULL

``


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