Quantcast
Channel: MaplePrimes - Questions and Posts tagged with system
Viewing all articles
Browse latest Browse all 164

Why does solve work with a system of equations, but then not with the same system written slightly differently?

$
0
0

I just tried to solve a very simple system of equations using solve but depending on how I write the system the command does out give any output. 

restart

solve({I__cm = m*r^2, r*T = I__cm*a/r, g*m-T = m*a}, {T, a})

solve({r*T = m*r^2*a*(1/r), g*m-T = m*a}, {T, a})

{T = (1/2)*m*g, a = (1/2)*g}

(1)

NULL

Solution with pencil and paper

T := (1/2)*m*g = (1/2)*m*gNULL

a := (1/2)*g = (1/2)*gNULL

Check this solution

evalb(g*m-T = m*a)

true

(2)

evalb(r*T = m*r^2*a*(1/r))

true

(3)

NULL


Notice that if I define I__cm then there is no solution being shown. I can rename I__cm to something else like y, still no output. Then in the second system I simply sub I__cm into the equation that has this variable, and it works.

So what's going on here? Why doesn't the first use of solve work?

Download solveSys.mw


Viewing all articles
Browse latest Browse all 164

Trending Articles