Mathematics Grade 10 15 min

Least common denominator

Least common denominator

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1

Introduction & Learning Objectives

Learning Objectives Identify the least common denominator (LCD) for two or more angle measures expressed in radians. Add and subtract angles in radians by first converting them to equivalent fractions with a common denominator. Apply the LCD to find positive and negative coterminal angles for a given angle in radians. Calculate the measure of a complementary or supplementary angle when the given angle is in radians. Solve geometric problems involving the sum or difference of sectors in a circle using the LCD. Ever tried to add one-third of a pizza to one-fourth of another? 🍕 You need a common way to slice them! The same idea is crucial when we combine angles on a circle. This tutorial connects a fundamental arithmetic skill, finding the least common denominator, to advanced...
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Key Concepts & Vocabulary

TermDefinitionExample RadianA unit of measure for angles, based on the radius of a circle. One radian is the angle created when the arc length is equal to the radius. A full circle is 2π radians.A 90° angle is equivalent to π/2 radians. A 180° angle is equivalent to π radians. Least Common Multiple (LCM)The smallest positive integer that is a multiple of two or more given integers.The LCM of 4 and 6 is 12, because 12 is the smallest number that both 4 and 6 divide into evenly. Least Common Denominator (LCD)The Least Common Multiple (LCM) of the denominators of two or more fractions. It's the smallest number you can use as a common denominator to add or subtract those fractions.For the fractions 1/4 and 5/6, the denominators are 4 and 6. The LCD is the LCM of 4 and 6, which is 12. Cot...
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Core Formulas

Adding/Subtracting Angles in Radians \frac{a\pi}{b} \pm \frac{c\pi}{d} = \frac{(ad \pm bc)\pi}{bd} To add or subtract angles expressed as fractions of π, you must first find a least common denominator (LCD) for the fractions. Convert each fraction to an equivalent fraction with the LCD, then add or subtract the numerators. Finding Coterminal Angles in Radians \theta_{coterminal} = \theta + 2\pi k, \text{ where k is any integer } (..., -2, -1, 0, 1, 2, ...) To find an angle coterminal with θ (in radians), add or subtract any integer multiple of 2π. When θ is a fraction, you must express 2π using the same denominator as θ. For example, to add 2π to π/3, you rewrite 2π as 6π/3. Finding a Supplementary Angle in Radians \theta_{supplement} = \pi - \theta To find the suppl...

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Sample Practice Questions

Challenging
An angle θ is supplementary to π/5. A second angle, φ, is coterminal with θ and lies in the interval [2π, 4π). What is the value of φ?
A.9π/5
B.4π/5
C.19π/5
D.14π/5
Challenging
Three adjacent sectors of a circle have central angles measuring π/4, 2π/3, and π/6. What is the total angle of the three sectors combined?
A.4π/13
B.13π/12
C.11π/12
D.4π/3
Challenging
The sum of two angles, α and β, is 11π/8 and their positive difference is 3π/8. What is the measure of the larger angle?
A.π/2
B.14π/8
C.7π/8
D.π

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