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Ch. 4 - Applications of Derivatives
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Not the one you use?Change textbook
Chapter 4, Problem 48

The range R of a projectile fired from the origin over horizontal ground is the distance from the origin to the point of impact. If the projectile is fired with an initial velocity at an angle with the horizontal, then in Chapter 13 we find that R-v_0^2/g(sin 2α) where g is the downward acceleration due to gravity. Find the angle α for which the range R is the largest possible.

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1
To find the angle \( \alpha \) that maximizes the range \( R \), we start with the given formula for the range: \( R = \frac{v_0^2}{g} \sin(2\alpha) \).
Recognize that the expression \( \sin(2\alpha) \) is maximized when \( \sin(2\alpha) = 1 \), because the sine function reaches its maximum value of 1.
Set \( \sin(2\alpha) = 1 \) to find the angle \( 2\alpha \). This occurs when \( 2\alpha = \frac{\pi}{2} + 2k\pi \), where \( k \) is an integer.
Solve for \( \alpha \) by dividing both sides of the equation \( 2\alpha = \frac{\pi}{2} \) by 2, giving \( \alpha = \frac{\pi}{4} \).
Thus, the angle \( \alpha \) that maximizes the range \( R \) is \( \frac{\pi}{4} \) radians, or 45 degrees.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Projectile Motion

Projectile motion refers to the motion of an object thrown or projected into the air, subject to only the acceleration of gravity. It involves two components: horizontal motion with constant velocity and vertical motion with constant acceleration due to gravity. Understanding these components is crucial for analyzing the trajectory and range of a projectile.
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Trigonometric Functions

Trigonometric functions, such as sine and cosine, are essential for resolving the components of projectile motion. In this context, the function sin(2α) is used to determine the range of the projectile. These functions help in calculating angles and distances in problems involving periodic phenomena or circular motion.
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Optimization in Calculus

Optimization involves finding the maximum or minimum values of a function. In this problem, we need to find the angle α that maximizes the range R of the projectile. This requires understanding how to use derivatives to find critical points and determine whether they correspond to maxima or minima, a fundamental concept in calculus.
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