Calculus Volume 3 · 免费预览

参数方程

参数方程分别把 x 和 y 表示为参数 t 的函数,因此曲线可能成环并重复经过自身路径,而且总是带有行进方向,而不必依附于单值函数。

1. Curves traced by a parameter

Curves traced by a parameter

2. Eliminating the parameter

Eliminating the parameter

3. Lines, circles, and ellipses

Lines, circles, and ellipses

4. The cycloid and orientation

The cycloid and orientation

5. What a parametric curve adds

Which statement best captures what a parametric curve allows that a graph of a single function y = f(x) does not?

6. Eliminating a linear parameter

The curve is given by x(t) = t - 1 and y(t) = 2t + 4 for all real t. What is its equation in x and y?

7. Circle and ellipse forms

Which pair of equations parametrizes the circle x squared plus y squared equals 16?

8. Orientation of a traced circle

For x = cos t and y = sin t restricted to 0 at most t at most 2 pi, starting at the point (1, 0), how is the circle traversed?

9. Height of a cycloid arch

For the cycloid x = r(t minus sin t) and y = r(1 minus cos t), what is the greatest height above the x axis?

10. The interval restricts the trace

Eliminating t from x = t squared and y = t on the interval from minus 1 to 2 gives y squared equals x. What curve is actually traced?

11. A coordinate from the parameter

For the parametrization x(t) = 2t + 1 and y(t) = 3t - 4, what value of y corresponds to x = 5? Give a number.

12. Radius from the equations

The parametrization x = 3cos t and y = 3 sin t traces a circle. What is its radius? Give a number.

13. A coordinate at a special angle

For x(t) = 4cos t and y(t) = 4 sin t, what is the value of x when t = pi? Give a number.

14. The direction of travel

What one-word name is given to the direction in which a parametric curve is traced as the parameter increases?

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