Run an Algorithm

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The term running an algorithm I use to mean doing a set of calculations:

What do you need to know to run an algorithm in an examination?

1. You need to understand the meanings of all variables to an extent that you are able to assign correct values to them.
2. You need to be able to write down the steps in the algorithm.
3. You need to be able to run the algorithm.

For example, here's a 'run' of the algorithm for solving for the forces at joint B in the Nodal Analysis key example:

Isolate Joint B
Apply vertical equilibrium: ${\textstyle \sum F_{y}=0}$ $9\sin {30}+F_{BD}\sin {30}-3-F_{BC}\sin {30}=0$ Substitute for: ${\textstyle \sin {30}=0.5}$ $9\times 0.5+0.5F_{BD}-3-0.5F_{BC}=-3-0$ $1.5+0.5F_{BD}-0.5F_{BC}=0$ Rearrange to find an expression for $F_{BD}$ $0.5F_{BD}=-1.5+0.5F_{BC}$ $F_{BD}=-3+F_{BC}$	Apply horizontal equilbrium: $\sum F_{x}=0$ $9\cos {30}+F_{BD}\cos {30}+F_{BC}\cos {30}=0$ Divide each term by $\cos {30}$: $9+F_{BD}+F_{BC}=0$ Substitute $F_{BD}=-3+F_{BC}$: $9+(-3+F_{BC})+F_{BC}=0$ $6+2F_{BC}=0$ $F_{BC}=-3kN$ (compression) Solve for $F_{BD}$: $F_{BD}=-3+F_{BC}$ $F_{BD}=-3-3=6kN$