From: the world has turned and left me here <shepardb@...>

Date: Fri, 12 Dec 1997 20:32:53 -0500 (EST)

Date: Fri, 12 Dec 1997 20:32:53 -0500 (EST)

There's another way to solve a set of 2 two-variable equations. It uses something called Cramer's rule, which you could probably find in a semi-advanced geometry or pre-calc class. You can break the rule down into variables that lower life-forms such as computers can interpret. FYI, the reason I know this is because I wrote a program for the TI-82 the does the same thing for a set of 3 three-variable equations. The math is a little different, but it shows the basic idea beheind the process. I could dig the program out (in *.82p form) is anyone is interested. HTH, Bryan Shepardson shepardb@... Mrs. Foster: Just remember, Father Mike, I own you. Father Mike: I work for God. Mrs. Foster: He works for me too. On Thu, 11 Dec 1997, Brian Victor wrote: > At 9:08 AM -0500 12/11/97, Chris wrote: > >>Does anyone know the answer to these two geometry questions? > >> > >>1. The formula for finding the intersection point of two lines. > >The intersection point of two lines is found by setting the two line > >equations equal to each other, solving for x and then substituting that > >value into one of the original equations to find y. > > That's exactly the concept. Getting it into BASIC is just a matter of > reducing it to two equality statements. For the moment, I'll assume that > your linear equations are in slope-intercept form. (y=mx+b) If they're > not, you'll have to add a step to get them there. For each equation, you > have two coefficients, and therefore two variables. > > y1 = ax + b > y2 = cx + d > > a, b, c, and d are your variables. Through algebra we can solve for x in a > form that will work nicely for an assignment statement. > > ax + b = cx + d > ax - cx = d - b > (a-c)x = d - b > x = (d-b)/(a-c) > > That last line will plug right into BASIC, with changes allowed for your > own particular variable names. Note however that it would be prudent to > make your x and y variables either single or double precision variables > (append either a # or a ! to the variable name: x# or x!) in order to allow > for the decimals that you're likely to run into. To locate the y > coordinate, take one of your original equations and plug in your x value, > which you now know: > > y = a * x + b > > This should solve your first problem for you. The second will be more of a > challenge. I'll look it over and see what I can come up with. > > -- Brian Victor > > > -- > To unsubscribe, send ANY message to <futurebasic-unsubscribe@...> >