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Cone cross-sections

Source: licencja: CC 0.

Przekroje stożka

Learning objectives

You will develop skills of communicating in English, basic mathematical, computer and scientific competences, learning skills.

You will learn to obtain cones and what are their properties.

You will learn to calculate elements of the cone using sections.

Learning effect

  • You will learn to obtain cones and what are their properties.

  • You will learn to calculate elements of the cone using sections.

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nagranie abstraktu

Revise previously learnt information about a coneconecone. The aim of the class is to learn about conic cross‑sections and calculating elements of the cone using cross‑sections.

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nagranie abstraktu

Analyse material presented in the slideshow. Pay attention to figures you obtain depending on the angle of inclination of the section of a coneconecone with a plane non‑parallel to the cone’s axis. Draw conclusions.

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Pokaz multimedialny - Przekroje stożka. Instrukcja obsługi z poziomu klawiatury: 1. Uruchomienie aplikacji - ENTER, 2. Na każdym ze slajdów czytany jest automatycznie tekst alternatywny po polsku, 3. Przy pierwszym uruchomieniu na pierwszym slajdzie, czytanie tekstu po angielsku - TAB, 4. Przejście między slajdami: do następnego slajdu - TAB, do poprzedniego slajdu - TAB + SHIFT, 5. Przejście do czytania napisu po angielsku - strzałka w górę + strzałka w dół (czyta tekst po angielsku widoczny na slajdzie).
Source: GroMar, licencja: CC BY 3.0.
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nagranie abstraktu

If the α angle of inclination of the plane of the section to the axis of the cones is:

  • 0°<α<45° then hyperbolahyperbolahyperbola

  • α=45° - parabola

  • 45°<α<90° - ellipseellipseellipse

  • α=90° - circlecirclecircle

  • 90°<α<135° - ellipse

  • α=135° - parabolaparabolaparabola

  • 135°<α<180° - hyperbola

  • α=180° - two intersecting lines

Task 1
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nagranie abstraktu

Look for information about conic sectionsconic sectionsconic sections in available sources. Write proper definitions. There are following conic sectionsconic sectionsconic sections, depending on the angle made by the cutting plane with the coneconecone axis and angle between the lateral and the cone axis.

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Source: GroMar, licencja: CC BY 3.0.
An ellipse
Definition: An ellipse
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nagranie abstraktu

An ellipseellipseellipse - is obtained when the angle between the cutting plane and the axis of the coneconecone is greater than the angle between the lateral and the cone axis.

A circle
Definition: A circle
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nagranie abstraktu

circlecirclecircle - is obtained when the cutting plane is perpendicular to the coneconecone axis.

A parabola
Definition: A parabola
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nagranie abstraktu

parabolaparabolaparabola - is obtained when the cutting plane is parallel to the lateral.

A hyperbola
Definition: A hyperbola
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nagranie abstraktu

hyperbolahyperbolahyperbola - is obtained when the angle between the cutting plane and the coneconecone axis is smaller than the angle between the cone axis and its lateral, or when the cutting plane is parallel to the cone axis but does not contain this axis.

Using obtained information do the following exercises.

Task 2
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nagranie abstraktu

Draw the axial section of a coneconecone whose angle of opening is 160° and the lateral is 8 cm. Calculate the radius of the base.

Task 3
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nagranie abstraktu

The cross‑section of a coneconecone is a circlecirclecircle whose radius is smaller than the radius of the cone’s base. Calculate the area of the cross‑section, knowing that the height of the cone is equal to 18 cm and the diameter of the base is 20 cm. The coneconecone was cut with a plane parallel to the base, 9 cm from the apex of the cone.

Task 4
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nagranie abstraktu

The axial section of a coneconecone is an isosceles triangle in which the angle between arms is 80°. The arm of this triangle is 12 cm long. Calculate the height and the radius of the base of the cone.

Task 5
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nagranie abstraktu

The angle between the lateral and the height of a coneconecone is 75°. The radius of the base of the cone is equal to 7 cm. Calculate the height of the cone.

Task 6
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nagranie abstraktu

Calculate the angle of opening of a coneconecone whose lateral is equal to 62 cm and the height is 5 cm.

Task 7

An extra task:

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nagranie abstraktu

Calculate the area of the axial section of a coneconecone whose height is 20 cm and tgα=4 (α - angle between the cone’s lateral and its radius).

After having completed all tasks, do the revision exercises.

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nagranie abstraktu

A figure that is the cross‑section of the coneconecone depends on the angle of inclination of the plane of the section to the cone axis:

  • If α=0 or α=180°, then we obtain two intersecting lines.

  • If α(0°,45°) or α(135°,180°), then we obtain a hyperbolahyperbolahyperbola.

  • If α(45°,90°) or α(90°,135°), then we obtain an ellipseellipseellipse.

  • If α=45° or α=135°, then we obtain a parabolaparabolaparabola.

  • If α=90°, then we obtain a circlecirclecircle.

Exercises

Exercise 1
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Wersja alternatywna ćwiczenia: Determine which sentences are true. Możliwe odpowiedzi: 1. As a result of cutting the cone with a plane perpendicular to the cone axis we obtain an ellipse., 2. A cone was cut with a plane that creates the angle 30° with the cone axis. As a result we obtained a hyperbola., 3. A parabola was obtained as a result of cutting a cone with a plane. The angle of inclination of the plane to the cone axis is smaller than 45°., 4. A cone was cut with a plane. As a result we obtained a circle. It means than the angle of inclination of the section to the cone axis is a right angle.
zadanie
Source: GroMar, licencja: CC BY 3.0.
Exercise 2

The Mountain of White Mist is shaped like a cone. The ski slope that goes from the top of the mountain to its base is 200 m long and its angle of inclination is 60°. How many minutes does a tourist need to walk around this mountain if the tourist walks with a speed 3,6 km/h?

Exercise 3

Describe in English what figure will be obtained as a result of cutting the cone with a plane inclined to the cone axis at the angle, depending on the angle.

Exercise 4
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Wersja alternatywna ćwiczenia: Indicate which pairs of expressions or words are translated correctly. Możliwe odpowiedzi: 1. stożek - cone, 2. przekrój stożka - cone’s section, 3. elipsa - ellipse, 4. koło - circle, 5. hiperbola - parabola, 6. parabola - hyperbola
zadanie
Source: GroMar, licencja: CC BY 3.0.
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Interaktywna gra, polegająca na łączeniu wyrazów w pary w ciągu jednej minuty. Czas zaczyna upływać wraz z rozpoczęciem gry. Jeden ruch to odkrywanie najpierw jednej potem drugiej karty z wyrazem. Każdy wyraz jest odczytywany. Kolejny ruch to odkrywanie trzeciej i czwartej karty. W ten sposób odsłuchasz wszystkie wyrazy. Nawigacja z poziomu klawiatury za pomocą strzałek, odsłuchiwanie wyrazów enterem lub spacją. Znajdź wszystkie pary wyrazów.
Source: Zespół autorski Politechniki Łódzkiej, licencja: CC BY 3.0.

Glossary

circle
circle

koło

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wymowa w języku angielskim: circle
cone
cone

stożek

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wymowa w języku angielskim: cone
cone’s axial section
cone’s axial section

przekrój osiowy stożka

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wymowa w języku angielskim: cone’s axial section
cone’s cross‑section
cone’s cross‑section

przekrój stożka

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wymowa w języku angielskim: cone’s cross‑section
conic sections
conic sections

krzywe stożkowe

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wymowa w języku angielskim: conic sections
ellipse
ellipse

elipsa

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wymowa w języku angielskim: ellipse
hyperbola
hyperbola

hiperbola

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wymowa w języku angielskim: hyperbola
parabola
parabola

parabola

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wymowa w języku angielskim: parabola

Keywords

circlecirclecircle

coneconecone

cone’s axial sectioncone’s axial sectioncone’s axial section

cone’s cross‑sectioncone’s cross‑sectioncone’s cross‑section

ellipseellipseellipse