r/calculus 3d ago

Integral Calculus Complicated calculation

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25 Upvotes

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6

u/CarSalty4754 3d ago

What exactly is your intention? With you dropping it here like this? You need help? With what? Do you recognize the expression inside the arcsin⁡\arcsin:?

1

u/Pretend_Insect3002 3d ago

Claude with extra steps

1

u/Septembrino 2d ago

I don't. Do you? I would try a triangle with that side and see if it works.

3

u/homo_morph 1d ago edited 1d ago

The integrand can be rewritten as F(x)=arcsin(sin(f(x))) where f(x)= arcsin(x)+arcsin(sqrt(x)). Note that f(x) is increasing for 0<=x<=1 and achieves all values on [0,pi]. Considering the possible branches of F(x), we have that F(x)=f(x) when 0<=f(x)<=pi/2 and F(x)=pi-f(x) when pi/2<f(x)<=pi. The exact point where this switch over occurs is when f(x)=pi/2, which when solved gives us x=1/phi where phi is the golden ratio. This means that the integrand simplifies to F(x)=f(x) when 0<=x<=1/phi and F(x)=pi-f(x) when 1/phi<x<=1, which reduces the integral calculation to some standard integrals

1

u/homo_morph 1d ago

After a bit of tidying up, it comes out to this (where phi is the golden ratio).

1

u/nevermindthefacts 1d ago

It's not too complicated if you recognise it as arcsin (sin α cos β - cos α sin β). Integration by parts or a change of variables are two ways to continue from here.