Swiss army knife equations

[Dave Britten]

The equation solver in the financial line (18C, 19B/BII, 17B/BII, 95LX, 100LX, 200LX) is vastly more sophisticated than the numeric solver offered by the scientifics, though you don't get any integration capability. It will actually try to solve symbolically, so you can potentially get very quick, accurate results. You can define temporary variables within equations, check which variable is being solved for, calculate inline sums, etc. It lets you do some pretty neat tricks. I'd recommend the palmtops, or 19BII if you want this solver, since you get the usual scientific functions in addition to finance (trig being the main advantage).

If you have a 48G, or the Solve Equation Library card for the 48SX, then the multiple equation solver really takes it to the next level. You can define a set of equations that share variables, and the solver will use them all simultaneously to find the variable you're after. For example, you can define 'P=V*I' and 'V=I*R', and it will deduce how to get amps directly from current and resistance, or voltage and resistance.

I have a set of four equations that allows solving triangles: 3 forms of the law of cosines expressed for different sides/angles, and one that expresses that the three angles total 180 degrees. From that, you just punch in your known values, and it'll find the remaining sides/angles for you.