18 Show that the volume V of a regular tetrahedron, all of whose side lengths are s, is V = s°V2 (all four %3D faces of a regular tetrahedron are equilateral triangles). Hence find the rate of increase of the surface area when the volume is 144V2 çm° and is increasing at a rate of 12 cm³/s.

Algebra & Trigonometry with Analytic Geometry
13th Edition
ISBN:9781133382119
Author:Swokowski
Publisher:Swokowski
Chapter4: Polynomial And Rational Functions
Section4.3: Zeros Of Polynomials
Problem 67E
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Question 18
dV
= 4ar-
dt
.2 dr
and hence find
dt
Show that
dr
in exact form when r = 10 cm.
dt
uing instead the methods of Section 9J, we begin with V = 40t.
Write r as a function of t, and hence write
dr
as a function of t.
dt
i Find the time when r = 10 cm, and hence find
dr
when r = 10 cm.
dt
ENRICHMENT
18 Show that the volume V of a regular tetrahedron, all of whose side lengths are s, is V = s³V2 (all four
faces of a regular tetrahedron are equilateral triangles). Hence find the rate of increase of the surface area
when the volume is 144V2 çm³ and is increasing at a rate of 12 cm³/s.
19 A large vase has a square base of side length 6 cm, and flat sides sloping outwards at an angle of 120°
with the base. Water is flowing in at 12 cm /s. Find, correct to three significant figures, the rate at which
the height of water is rising when the water has been flowing in for 3 seconds.
Transcribed Image Text:dV = 4ar- dt .2 dr and hence find dt Show that dr in exact form when r = 10 cm. dt uing instead the methods of Section 9J, we begin with V = 40t. Write r as a function of t, and hence write dr as a function of t. dt i Find the time when r = 10 cm, and hence find dr when r = 10 cm. dt ENRICHMENT 18 Show that the volume V of a regular tetrahedron, all of whose side lengths are s, is V = s³V2 (all four faces of a regular tetrahedron are equilateral triangles). Hence find the rate of increase of the surface area when the volume is 144V2 çm³ and is increasing at a rate of 12 cm³/s. 19 A large vase has a square base of side length 6 cm, and flat sides sloping outwards at an angle of 120° with the base. Water is flowing in at 12 cm /s. Find, correct to three significant figures, the rate at which the height of water is rising when the water has been flowing in for 3 seconds.
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Author:
Swokowski
Publisher:
Cengage