Answer:
The rate of change in the area beneath the ladder is 5.25 ft²/s
Step-by-step explanation:
Area of triangle is given by;
[tex]A = \frac{1}{2}bh\\\\2A = bh\\\\take \ derivative \ of \ both \ sides \ with \ respect \ to \ "t"\\\\2\frac{dA}{dt} = h\frac{db}{dt} + b\frac{dh}{dt}\\\\divide \ through \ by \ 2\\\\\frac{dA}{dt} = (\frac{h}{2} )\frac{db}{dt} + (\frac{b}{2}) \frac{dh}{dt}[/tex]
where;
b is the base of the triangle, given as 6 ft
h is the height of the triangle, determined by applying Pythagoras theorem.
h² = 10² - 6²
h² = 100 - 36
h² = 64
h = √64
h = 8 ft
Determine the rate of change of the height;
[tex]h^2 + b^2 = 10^2\\\\h^2 + b^2 =100\\\\2h\frac{dh}{dt} + 2b\frac{db}{dt} =0\\\\h\frac{dh}{dt} + b\frac{db}{dt} =0\\\\h \frac{dh}{dt} = -b\frac{db}{dt} \\\\\frac{dh}{dt} = (\frac{-b}{h} )\frac{db}{dt}\\\\\frac{dh}{dt} =(\frac{-6}{8})(3)\\\\\frac{dh}{dt} = -\frac{9}{4} \ ft/s[/tex]
Finally, determine the rate of change of area beneath the ladder;
[tex]\frac{dA}{dt} = (\frac{h}{2} )\frac{db}{dt} + (\frac{b}{2}) \frac{dh}{dt}\\\\\frac{dA}{dt} = (\frac{8}{2} )(3) + (\frac{6}{2}) (\frac{-9}{4})\\\\\frac{dA}{dt} = 12 - \frac{27}{4} \\\\\frac{dA}{dt} = \frac{48-27}{4}\\\\\frac{dA}{dt} = \frac{21}{4} \ ft^2/s\\\\\frac{dA}{dt} = 5.25 \ ft^2/s[/tex]
Therefore, the rate of change in the area beneath the ladder is 5.25 ft²/s
