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Section 5.3
How is this done?
Tomorrow morning we finish Section 5.3.
How is this done?
Tomorrow morning we finish Section 5.3.
the area of rectangle inscribed in one arc of the graph A=2x*cos(x), 0<x<pi/2
let P be a point on the curve where rectangle touches curve
coordinates are P(x,2x*cos(x))
sides of the rectangle are
2x-> the length
y=2x*cos(x)->the height
to find max area, you need take derivative of A=2x*cos(x)
(d/dx)(2x*cos(x))=2 (cos(x) - x sin(x))
equal to zero
2 (cos(x) - x sin(x))=0
cos(x) - x* sin(x)=0....use calculator
x=0.86
then area is
A=2*0.86*cos(0.86)=1.1221924452421692
A=1.122
b.
find x for what A>=1
2x*cos(x)>=1/(2x), 0<x<pi/2
cos(x)>=1/(2x)...use calculator
0.610031<= x <=1.09801
Interval notation
[0.610031, 1.09801]
To find the value of x that gives an area A maximum, we need to find the first derivative dA/dx (A is a function of x). If A has a maximum value, it happens at x such that dA/dx = 0
also, you have derivative in pre calculus
take a look
https://philschatz.com/precalculus-book/contents/m49455.html
you can approximate using a graph
as you can see, x is half way between 0 and pi/2
so x=pi/4
the length of rectangle is 2x=2(pi/4)=pi/2, the height is x=pi/4
A=(pi/2)(pi/4)=1.2337005501