A piece of wire, of length 40 cm, is bent to form a sector of a circle
Question:
A piece of wire, of length 40 cm, is bent to form a sector of a circle with radius rcm and sector angle θ radians, as shown in the diagram. The total area enclosed by the shape is A cm2.
a. Express θ in terms of r.
b. Show that A = 20r − r2.
c. Find the value of r for which there is a stationary value of A.
d. Determine the magnitude and nature of this stationary value.
0 r
Step by Step Answer:
a The length of the wire is equal to the circumference of the circle which is 2r ...View the full answer
Cambridge International AS And A Level Mathematics Pure Mathematics 1 Coursebook
ISBN: 9781108407144
1st Edition
Authors: Sue Pemberton, Julian Gilbey
Related Video
The area of a circle is given by the formula: A = ?r^2 Where A is the area, ? is a mathematical constant (approximately 3.14), and r is the radius of the circle. The radius is the distance from the center of the circle to the edge. So for example, if the radius of a circle is 5 units, the area would be: A = ?(5^2) = ?(25) = 78.5 square units Here three friends went out to a restaurant and decided to have pizza for lunch. While they were waiting for their order, one of them stepped out to take a call but promised to return in two minutes. The waiter came and presented them with the menu, and they decided to order two 10-inch pepperoni pizzas. The waiter took their order and left. Just then, the third friend returned and asked what they had ordered. They explained that they had ordered two small pepperoni pizzas as they were only three of them and it would be enough for them. However, the third friend suggested that for the same price, they could get a large pizza that would be much bigger than the two small ones. He asked the waiter for a pen and paper and proceeded to calculate the area of the two small pizzas and compared it to the area of one large pizza. The friends were amazed at how the circle measurements worked and decided to change their order from two small pizzas to one large pizza.
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