What are the points of inflection of #f(x)=x^3sin^2x # on the interval #x in [0,2pi]#?

Answer 1

The successive graphs reveal POI at x = 0, +-1.24, +-2.55, +-3.68, +-4.82, ....

#f=1/2x^3(1-cos 2x)#, giving x-intercepts #0, 0, +-pi, +-2pi, +-3pi, ...#
#f''=1/2((x^3)''-(x^3cos2x)'')#
#=x(3-(3cos2x-6xsin2x-2x^2cos2x))#

With the exception of x = 0, all of f''s zeros cannot be

attained with exact mathematical precision.

However, we are able to find them in pairs between

#(kpi. (k+1)pi) and (-(k+1)pi, -kpi), k = 1, 2, 3, ---#, respectively.
There are 4 POI, for #x in (0. 2pi)#.

1.24, 2.55, 3.58, and 4.82 are almost exactly the same.

A graphical method has been used to obtain some locations near O.

utilizing the proper ranges and subdomains.

graph{x^3sinx[-20, 20, -10, 10]}

Graph 1: The graph exhibits symmetry around O.

graph{x^3sinxsinx [0, 6.28, -50, 300]} Graph 2: Four points of interest and the power-growth of y's local maxima are revealed

graph{x^3sinxsinx [1.24 1.26, -10, 10]} Figure 3: finds a point of interest close to 1.24.

A POII is located in the vicinity of 2.55, as shown in graph{x^3sinxsinx [2.54, 2.56,-10, 10]}.

graph{x^3sinx[4.81 4.83, 0, 200]}

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Answer 2

To find the points of inflection, we need to find where the second derivative changes sign. The second derivative of f(x)=x3sin2(x) f(x) = x^3 \sin^2(x) is:

f(x)=6xsin2(x)+2x3sin(x)cos(x)f''(x) = 6x \sin^2(x) + 2x^3 \sin(x) \cos(x)

The points of inflection occur where f(x)=0 f''(x) = 0 or is undefined, and where f(x) f''(x) changes sign. Solving f(x)=0 f''(x) = 0 and analyzing the sign changes on the interval [0,2π][0, 2\pi] will give us the points of inflection.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

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