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Shocker 
Posted: January 15, 2011 11:52 pm

Forum Addict ++ Group: Trusted Members Posts: 1,631 Member No.: 3,558 Joined: November 06, 2005 
I use the solvers on my calculators when it takes more than a second to rearrange.
I have been trying to get my calculator to solve this equation. (1/Tan(50))  (1/Tan(X)) = 0.2 When i first got my calculator to do this hours ago, i got 57.417. Which is the correct answer. Now when i do the same thing i get, 662.583 every time. Technically this is also a correct answer but it is 720 out, which is 2 full rotations (2x360). Why would it now give me this answer? I really don't understand......I haven't changed any settings, so they should be exactly the same. I got my graphical calculator out to see what that says and at first it gave me the answer 122. Which i have no idea how that relates to the answer that i am looking for. I left it alone whilst i typed this out and i gave it another go to get the 122 value to put in this topic but then it started to give me 57.417 (Reason why 122 isn't as accurate as the other values). I haven't changed anything. I have also set up my graphical calculator up the same as my other calculator. I am so confused about this right now!! When i am in a real rush and don't have the time to rearrange equations (as it's not my strongest ability by far), i rely on the solvers so much. So i'd like to resolve this little discrepancy. Lol, i tried to get my nongraphical calculator to solve the equation again, guess what.......it now says 57.417. My calculator turned itself off to save the battery. All i did was turn it on and reentered the equation. Lol, this aint even funny! Does anyone know of any knowledge that could enlighten me about why it is doing this? I know that once the equation is balanced it will spit out the value used to balance it. But surely if the calculator runs the same algorithm to balance the equation then surely the it should always spit out the same value for the same equation........... I have found one thing though, when trying to use the solver on the calculator. It tries to use the value already in X to see if its the answer for X for the equation. So the first time it solves an equation it might take a little while. So long as you don't change X and ask it to solve the exact same equation, it takes a split second to spit an answer out. 
Village Idiot 
Posted: January 16, 2011 04:18 am

Forum Addict ++ Group: Trusted Members Posts: 1,665 Member No.: 11,398 Joined: October 08, 2007 
Solvers need some kind of starting value to work with (probably the X value, judging by your description). The first time you ran it, you had a different initial value than when you ran it the second time. If there are multiple correct solutions, the one that the solver converges to will depend on what the initial value was. When the power was cycled, everything reset, and so it gave you the same answer as it did the first time.

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