Mathematics
Grade 10
15 min
What decimal number is illustrated?
What decimal number is illustrated?
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1
Introduction & Learning Objectives
Learning Objectives
Interpret a decimal value from a geometric construction on a number line, such as the construction of √2.
Determine the decimal representation of a trigonometric ratio illustrated in a right-angled triangle or on the unit circle.
Calculate the decimal coordinates of intersection points illustrated by graphs of lines and circles.
Analyze a visual representation of an infinite geometric series and determine the repeating decimal it represents.
Differentiate between the exact value of an illustrated number (e.g., π, √3) and its decimal approximation.
Apply the Pythagorean theorem to find the exact and approximate decimal length illustrated by the hypotenuse of a right triangle.
Ever wondered how you can 'draw' a number like √2 perfectly using just...
2
Key Concepts & Vocabulary
TermDefinitionExample
Irrational NumberA number that cannot be expressed as a simple fraction (a/b, where a and b are integers). Its decimal representation is non-repeating and non-terminating.The number π is irrational. Its decimal form is approximately 3.14159... and continues infinitely without a repeating pattern.
Geometric ConstructionThe process of drawing points, lines, and circles using only a compass and a straightedge. It allows for the precise illustration of lengths that can be irrational.Constructing a square with a side length of 1, then drawing its diagonal. The length of that diagonal is exactly √2.
Unit CircleA circle with a radius of 1 centered at the origin (0,0) of a Cartesian plane. It is used to visualize trigonometric functions.The point on the unit circle correspon...
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Core Formulas
Pythagorean Theorem for Lengths
c = \sqrt{a^2 + b^2}
Use this formula to find the length of the hypotenuse (c) when the lengths of the two legs (a and b) of a right triangle are known. This is often used in geometric constructions to find irrational lengths.
Sum of an Infinite Geometric Series
S = \frac{a_1}{1 - r}, \text{ for } |r| < 1
Use this to find the sum (S) of an infinite geometric series, where a₁ is the first term and r is the common ratio. This is the key to converting illustrations of repeating decimals into their fractional form.
Unit Circle Coordinates
(x, y) = (\cos(\theta), \sin(\theta))
The x and y coordinates of any point on the unit circle can be found using the cosine and sine of the angle (θ) formed with the positive x-axis. This illustrates h...
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Challenging
An illustration shows a path on the face of a cube with side length 2. A point starts at a vertex and travels a distance of 1 unit along an edge. It then turns 90° and travels 1/3 of the previous distance. It turns 90° again and travels 1/3 of the *new* previous distance, and so on, spiraling inward. What is the decimal number illustrated by the total length of this infinite path?
A.1.333
B.2.0
C.3.0
D.1.5
Challenging
A graph shows two intersecting circles. Circle 1 is centered at (0,0) with radius \sqrt{10}. Circle 2 is centered at (5,0) with radius \sqrt{5}. What is the decimal value of the x-coordinate of their intersection points?
A.1.0
B.2.0
C.3.0
D.4.0
Challenging
On a unit circle, a point P starts at (1,0). It rotates counter-clockwise by an angle of 60°, then by an additional 30°, then by an additional 15°, and so on, with each subsequent rotation being half the previous. What is the decimal value of the y-coordinate of the final position of P, rounded to three decimal places?
A.1.000
B.0.866
C.0.500
D.0.707
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