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MATH 119 MIDTERM REVIEW. 2010 Outreach Trip. Summary Date Aug 20 – Sept 4 Location Cusco, Peru # Students 22 Project Cost $16,000. Building Projects Kindergarten Classroom provides free education Sewing Workshop enables better job prospects
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2010 Outreach Trip Summary Date Aug 20 – Sept 4 Location Cusco, Peru # Students 22 Project Cost $16,000 Building Projects Kindergarten Classroom provides free education Sewing Workshop enables better job prospects ELT Classroom enables better job prospects More info @ studentsofferingsupport.ca/blog
Tutor: Maysum Panju • 3B Computational Mathematics • Lots of tutoring experience • Interests: • Reading • Pokémon • Calculus
Outline • Approximating Things • Newton’s Method, Fixed-Point Iteration • Guessing with Polynomials • Interpolating Polynomials, Taylor Polynomials, Taylor’s Remainder Theorem • Very Big Sums • Infinite Series, Convergence Tests, Power Series • Questions?
Writing Solutions A good solution includes… • An introductory statement: what you are given and what you have to show/find; • A concluding statement: summarize the conclusion briefly; • Justifications of the main steps: refer to definitions, rules, and known properties; • Some sentences of guidance for the reader, e.g. how you are going to solve the problem.
Newton’s Method • An iterativemethod for finding roots of a function. • Guess a root. • Find the tangent line there. • Find the x-intercept of the tangent line. • This is your new guess! • Repeat. • Formulaically:
Fixed Point Method • An iterative method for finding a solution to an equation of the form • Guess a solution • Compute • This is your new guess! • Repeat. • Won’t always converge! To be safe, require that on the interval you are working in,
Fixed Point Example Suppose you want to find a root of Which of the following choices of will give a good fixed point iteration?
Pictures Newton Method Fixed Point Iteration
Interpolating Polynomials • Given data points Find a polynomial that goes through all of them. (Called an “interpolant”.) • Why? Polynomials are “easy”. • Fact: Given n points, there is a unique polynomial of degree at most n – 1passing through them. • Fact: Polynomials frequently give bad approximations, especially far from the data.
Newton Interpolation • Find a polynomial that goes through the points which are equally spaced with a distance of h units betweenand • Construct a table of differences. • Fit into the polynomial template.
Interpolation Example • Suppose your data points are What is an estimate for f (2.25)?
Lagrange Linear Interpolation • When guessing the function betweentwo known points… • Assume the function is just a line that connects the two dots. • Such a simple concept!!!! (Such an annoying formula!) • Given two points and , set
This time, be linear. • Suppose your data points are What is an estimate for f (2.25)?
Taylor Polynomial • Given information about a curve at a specific point, approximate it for the surrounding area. • Use values of higher derivatives: When a = 0, this is called a Maclaurin Polynomial.
Taylor’s Inequality • An approximation is only as good as the error bound. • Error function: where is an upper bound forbetween x and a
Taylor ApproximationExample • Compute using a quadratic Taylor polynomial. Bound the error.
Taylor Series Exercise • Find Taylor Polynomials (around x=0) for…
Infinite Series • Sums of infinitely many terms. • Example: Taylor Series! • Two main questions: • Does the series converge? …. Hard • What does the series converge to? … VERY Hard • We focus on (1) … in general, work with infinite series is an art, not a science.
Convergence Tests • Divergence test: • A series can only converge if the terms get small. • RatioTest: • A series can only converge if the terms keep getting smaller.
Convergence Tests • Integral test: • A series converges exactly when the equivalent integral does. • P series test: • Sums of powers converge only for small powers.
Convergence Tests • Alternating Series test: • An alternating series converges if the terms keep getting smaller. if • The error in this case is
Infinite Series Practice • Which converge?