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Click to edit Master title style Click to edit Master subtitle style * * * Roots of a Nonlinear Equation Topic: Newton-Raphson Method Major: General Engineering http://numericalmethods.eng.usf.edu * * * Newton-Raphson Method http://numericalmethods.eng.usf.edu f(x) f(xi) f(xi-1) � EMBED Equation.3 ��� xi+2 xi+1 xi X _1075143848.unknown * * * Derivation http://numericalmethods.eng.usf.edu f(x) f(xi) A C B xi+1 xi X * * * Algorithm for Newton-Raphson Method http://numericalmethods.eng.usf.edu * * * Step 1 Evaluate f(x) symbolically http://numericalmethods.eng.usf.edu * * * Step 2 Calculate the next estimate of the root Find the absolute relative approximate error http://numericalmethods.eng.usf.edu * * * Step 3 Find if the absolute relative approximate error is greater than the pre-specified relative error tolerance. If so, go back to step 2, else stop the algorithm. Also check if the number of iterations has exceeded the maximum number of iterations. http://numericalmethods.eng.usf.edu * * * Example You are working for ‘DOWN THE TOILET COMPANY’ that makes floats for ABC commodes. The ball has a specific gravity of 0.6 and has a radius of 5.5 cm. You are asked to find the distance to which the ball will get submerged when floating in water. http://numericalmethods.eng.usf.edu * * * Solution The equation that gives the depth ‘x’ to which the ball is submerged under water is given by Use the Newton’s method of finding roots of equations to find the depth ‘x’ to which the ball is submerged under water. Conduct three iterations to estimate the root of the above equation. http://numericalmethods.eng.usf.edu * * * Graph of function f(x) http://numericalmethods.eng.usf.edu * * * Iteration #1 http://numericalmethods.eng.usf.edu * * * Iteration #2 http://numericalmethods.eng.usf.edu * * * Iteration #3 http://numericalmethods.eng.usf.edu * * * Advantages Converges fast, if it converges Requires only one guess http://numericalmethods.eng.usf.edu * * * Drawbacks Inflection Point http://numericalmethods.eng.usf.edu Chart1 -64 -54.872 -46.656 -39.304 -32.768 -27 -21.952 -17.576 -13.824 -10.648 -8 -5.832 -4.096 -2.744 -1.728 -1 -0.512 -0.216 -0.064 -0.008 0 0.008 0.064 0.216 0.512 1 1.728 2.744 4.096 5.832 8 0 -8 -8 0 0 -2.37037037 -2.37037037 0 0 -0.702334595 -0.702334595 0 1 2 3 f(x) x Sheet1 f(x)=(x-1)^3 inflection point pitfall in Newton_raphson Method -3 -64 -2.8 -54.872 -2.6 -46.656 -2.4 -39.304 -2.2 -32.768 -2 -27 -1.8 -21.952 -1.6 -17.576 -1.4 -13.824 -1.2 -10.648 -1 -8 -0.8 -5.832 -0.6 -4.096 -0.4 -2.744 -0.2 -1.728 0 -1 0.2 -0.512 0.4 -0.216 0.6 -0.064 0.8 -0.008 1 0 1.2 0.008 1.4 0.064 1.6 0.216 1.8 0.512 2 1 2.2 1.728 2.4 2.744 2.6 4.096 2.8 5.832 3 8 -1 0 -1 -8 -1 -8 -0.3333333333 0 -0.3333333333 0 -0.3333333333 -2.37037037 -0.3333333333 -2.37037037 0.11111 0 0.11111 0 0.11111 -0.702334595 0.11111 -0.702334595 0.40741 0 Sheet1 Sheet2 Sheet3 * * * Drawbacks (continued) Division by zero http://numericalmethods.eng.usf.edu Chart10 -0.0001976 -0.0001096 -0.0000516 -0.0000176 -0.0000016 0.0000024 0.0000004 -0.0000016 0.0000024 0.0000184 0.0000524 -0.0000016 -0.0000016 0.02 x f(x) Sheet1 -0.05 -0.0001976 -0.04 -0.0001096 -0.03 -0.0000516 -0.02 -0.0000176 -0.01 -0.0000016 0 0.0000024 0.01 0.0000004 0.02 -0.0000016 0.03 0.0000024 0.04 0.0000184 0.05 0.0000524 0.02 -0.0000016 0 -0.0000016 -0.63069 -0.5897021566 0 0 1 0.8414709848 2 0.9092974268 3 0.1411200081 4 -0.7568024953 5 -0.9589242747 6 -0.2794154982 7 0.6569865987 8 0.9893582466 9 0.4121184852 10 -0.5440211109 0.5499 0.5226 0.5499 0 0.5499 0.5226 0 0 4.462 0 4.462 -0.9688 4.462 0 7.53982 0.951 7.53982 0 7.53982 0.951 4.462 -0.9688 0.5499 0 Sheet1 -0.5897021566 0 0.8414709848 0.9092974268 0.1411200081 -0.7568024953 -0.9589242747 -0.2794154982 0.6569865987 0.9893582466 0.4121184852 -0.5440211109 0.5226 0 0.5226 0 0 -0.9688 0 0.951 0 0.951 -0.9688 0 -0.063069 0.5499 4.462 7.53982 x f(x) Sheet2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.02 x F(x) Sheet3 * * * Drawbacks (continued) Root Jumping http://numericalmethods.eng.usf.edu Chart3 -0.5897021566 0 0.8414709848 0.9092974268 0.1411200081 -0.7568024953 -0.9589242747 -0.2794154982 0.6569865987 0.9893582466 0.4121184852 -0.5440211109 0.5226 0 0.5226 0 0 -0.9688 0 0.951 0 0.951 -0.9688 0 -0.063069 0.54990 4.462 7.53982 x f(x) Sheet1 -0.1 -0.0012976 -0.09 -0.0009696 -0.08 -0.0007016 -0.07 -0.0004876 -0.06 -0.0003216 -0.05 -0.0001976 -0.04 -0.0001096 -0.03 -0.0000516 -0.02 -0.0000176 -0.01 -0.0000016 0 0.0000024 0.01 0.0000004 0.02 -0.0000016 0.03 0.0000024 0.04 0.0000184 0.05 0.0000524 0.06 0.0001104 0.07 0.0001984 0.08 0.0003224 0.09 0.0004884 0.1 0.0007024 -0.63069 -0.5897021566 0 0 1 0.8414709848 2 0.9092974268 3 0.1411200081 4 -0.7568024953 5 -0.9589242747 6 -0.2794154982 7 0.6569865987 8 0.9893582466 9 0.4121184852 10 -0.5440211109 0.5499 0.5226 0.5499 0 0.5499 0.5226 0 0 4.462 0 4.462 -0.9688 4.462 0 7.53982 0.951 7.53982 0 7.53982 0.951 4.462 -0.9688 0.5499 0 Sheet1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 -0.063069 0.5499 4.462 7.53982 x f(x) Sheet2 Sheet3 * * * Drawbacks (continued) Oscillations near Local Maxima or Minima http://numericalmethods.eng.usf.edu Chart1 6 5.24 4.56 3.96 3.44 3 2.25 2 2.25 3 3.44 3.96 4.56 5.24 6 6.84 7.76 8.76 9.84 11 12.24 0 5.0625 0 2.25 0 3 3 0 0 5.0625 0 2.092416 2.092416 0 0 2.25 3 4 2 1 -1.75 -0.3040 0.5 3.142 f(x) x Sheet1 -2 6 -1.8 5.24 -1.6 4.56 -1.4 3.96 -1.2 3.44 -1 3 -0.5 2.25 0 2 0.5 2.25 1 3 1.2 3.44 1.4 3.96 1.6 4.56 1.8 5.24 2 6 2.2 6.84 2.4 7.76 2.6 8.76 2.8 9.84 3 11 3.2 12.24 -1.75 0 -1.75 5.0625 -1.75 0 0.5 2.25 -1 0 -1 3 -1 3 0.5 0 -0.304 0 -1.75 5.0625 -0.304 0 -0.304 2.092416 -0.304 2.092416 3.142 0 0.5 0 0.5 2.25 Sheet1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 3 1 4 f(x) x Sheet2 Sheet3 http://numericalmethods.eng.usf.edu http://numericalmethods.eng.usf.edu http://numericalmethods.eng.usf.edu http://numericalmethods.eng.usf.edu http://numericalmethods.eng.usf.edu http://numericalmethods.eng.usf.edu http://numericalmethods.eng.usf.edu http://numericalmethods.eng.usf.edu http://numericalmethods.eng.usf.edu http://numericalmethods.eng.usf.edu http://numericalmethods.eng.usf.edu http://numericalmethods.eng.usf.edu http://numericalmethods.eng.usf.edu http://numericalmethods.eng.usf.edu http://numericalmethods.eng.usf.edu http://numericalmethods.eng.usf.edu http://numericalmethods.eng.usf.edu http://numericalmethods.eng.usf.edu
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