Polynomial Interpolation and Its Error Term · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

One polynomial through the points

Mathematics · Calculus & Analysis · ages 20-21
Name ______________________   Date ____________
  1. The straight line through (1, 2) and (3, 8) interpolates the data. What value does it give at x equal 2?

    Answer: ______________

  2. Three data points have distinct x values zero, one and two. What is the largest degree the interpolating polynomial can have?

    • 1
    • 3
    • 2
    • 4
  3. Three data points have distinct x values 0, 1 and 2. What is the largest degree the interpolating polynomial can have?

    • 1
    • 2
    • 3
  4. Using more and more equally spaced points always makes the worst interpolation error smaller.

    Circle one:   True   False

  5. Which formula gives the linear interpolation error at distinct nodes x0 and x1?

    • f(x) - p(x) = f''(xi) / 2 times (x - x0)(x - x1)
    • f(x) - p(x) = f''(xi) times (x - x0) + (x - x1)
    • f(x) - p(x) = f'(xi) times (x - x0)(x - x1)
  6. For distinct nodes x0 and x1, which formula gives the linear interpolation error?

    • f prime of xi times (x minus x0) times (x minus x1)
    • f(x) minus p(x) equals f double prime of xi times (x minus x0) plus (x minus x1)
    • f(x) minus p(x) equals f double prime of xi times (x minus x0) times (x minus x1)
    • f(x) minus p(x) equals f double prime of xi divided by 2 times (x minus x0) times (x minus x1)
  7. For the data points (0, 1) and (2, 9), what is the first divided difference of f over these nodes?

    • 4
    • 5
    • 8
    • 10
  8. For the points (0, 1) and (2, 9), what is the first divided difference?

    • 2
    • 4
    • 8
  9. With nodes 0, 1 and 2, the first Lagrange basis piece is (x - 1)(x - 2) / 2. What is its value at x = 0.5?

    Answer: ______________

  10. Two different polynomials, each of degree at most 2, pass through the same three points with distinct x coordinates. Is that possible?

    Circle one:   True   False

LightMySky · lightmysky.comW1-mt_NSnzY9Xodd-s1

Answer key

For grown-ups. Fold this page away before handing over the rest.

One polynomial through the points W1-mt_NSnzY9Xodd-s1

  1. 5 · The midpoint of the segment joins values 2 and 8, giving 5.
  2. 2 · Three points determine a polynomial of degree at most 2.
  3. 2 · Three points fix degree two.
  4. False · Runge showed equally spaced points can oscillate worse near the ends.
  5. f(x) - p(x) = f''(xi) / 2 times (x - x0)(x - x1) · Second derivative over 2 times the product of distances to the nodes.
  6. f(x) minus p(x) equals f double prime of xi divided by 2 times (x minus x0) times (x minus x1) · The error equals the second derivative at an interior point, divided by 2, times the nodal product.
  7. 4 · The divided difference is (9 minus 1) divided by (2 minus 0), which is 4.
  8. 4 · Slope between the points: 8 over 2 is 4.
  9. 0.375 · Minus 0.5 times minus 1.5 over 2 is 0.375.
  10. False · Impossible. Their difference would be a degree at most 2 polynomial with three roots, hence zero.
Worksheet · LightMySky