Document Sample

GEOMETRY EXERCISES 1. Describe the regions of space given by the following vector equations. In each, r denotes the vector xi + yj + zk; ‘·’ and ∧ denote the scalar (dot) and vector (cross) product: • r∧ (i + j) = (i − j) , • r · i = 1, • |r − i| = |r − j| , • |r − i| = 1, • r · i = r · j = r · k, • r ∧ i = i. 2. Find the shortest distance between the lines x−1 y−3 z y−1 = = and x = 2, = z. 2 3 2 2 [Hint: parametrise the lines and write down the vector between two arbitrary points on the lines; then determine when this vector is normal to both lines.] 3. Let Lθ denote the line through (a, b) making an angle θ with the x-axis. Show that Lθ is a tangent of the parabola y = x2 if and only if tan2 θ − 4a tan θ + 4b = 0. [Hint: parametrise Lθ as x = a + λ cos θ and y = b + λ sin θ and determine when Lθ meets the parabola precisely once.] Show that the tangents from (a, b) to the parabola subtend an angle π/4 if and only if 1 + 24b + 16b2 = 16a2 . [Hint: use the formula tan(θ1 − θ2 ) = (tan θ1 − tan θ2 )/(1 + tan θ1 tan θ2 ).] Sketch the curve 1 + 24y + 16y 2 = 16x2 and the original parabola on the same axes. 4. What transformations of the xy-plane do the following matrices represent: µ ¶ µ ¶µ ¶ µ ¶ µ ¶µ ¶ x 1 0 x x 2 0 x i) 7→ , ii) 7→ , µ y ¶ µ 0 −1 y ¶µ ¶ µ y ¶ µ 0 1 y ¶µ ¶ x 1/2 1/2 x x cos θ − sin θ x iii) 7→ , iv) 7→ . y 1/2 1/2 y y sin θ cos θ y Which, if any, of these transformations are invertible? 5. The cycloid is the curve given parametrically by the equations x (t) = t − sin t, and y (t) = 1 − cos t for 0 ≤ t ≤ 2π. (a) Sketch the cycloid. (b) Find the arc-length of the cycloid. (c) Find the area bounded by the cycloid and the x-axis. (d) Find the area of the surface of revolution generated by rotating the cycloid around the x-axis. (e) Find the volume enclosed by the surface of revolution generated by rotating the cycloid around the x-axis.

DOCUMENT INFO

Shared By:

Categories:

Stats:

views: | 10 |

posted: | 3/9/2010 |

language: | English |

pages: | 1 |

Description:
GEOMETRY EXERCISES 1 Describe the regions of space given by the

OTHER DOCS BY etssetcf

How are you planning on using Docstoc?
BUSINESS
PERSONAL

By registering with docstoc.com you agree to our
privacy policy and
terms of service, and to receive content and offer notifications.

Docstoc is the premier online destination to start and grow small businesses. It hosts the best quality and widest selection of professional documents (over 20 million) and resources including expert videos, articles and productivity tools to make every small business better.

Search or Browse for any specific document or resource you need for your business. Or explore our curated resources for Starting a Business, Growing a Business or for Professional Development.

Feel free to Contact Us with any questions you might have.