A belongs to b, b subset c, a not a subset of c

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Homework Statement


a∈b, b⊆c, a not ⊆ c
(in other words, the last subset symbol should have a line from top to bottom)

Homework Equations




none

The Attempt at a Solution



ive tried a million things, I can't find anything that doesn't break one of the conditions

the most recent attempt is that
A, B and C are all empty sets, but that would imply that a can be an element of B. my logic is that a doesn't contain all the elements of c, because there are no elements of c

every other thing I've tried has c containing all the elements of B, but since B contains all the elements of A, i run into a logical problem.

I tried for a long time on this one, and I really need help
 
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This might be an exercise in understanding what ∈ and ⊆ mean, but I'm not sure if you copied the problem correctly. Are you sure that's what it reads?
 
Consider b= {1, 2, 3}, c= {1, 2, 3, 4}, a= 1.
 
Prove $$\int\limits_0^{\sqrt2/4}\frac{1}{\sqrt{x-x^2}}\arcsin\sqrt{\frac{(x-1)\left(x-1+x\sqrt{9-16x}\right)}{1-2x}} \, \mathrm dx = \frac{\pi^2}{8}.$$ Let $$I = \int\limits_0^{\sqrt 2 / 4}\frac{1}{\sqrt{x-x^2}}\arcsin\sqrt{\frac{(x-1)\left(x-1+x\sqrt{9-16x}\right)}{1-2x}} \, \mathrm dx. \tag{1}$$ The representation integral of ##\arcsin## is $$\arcsin u = \int\limits_{0}^{1} \frac{\mathrm dt}{\sqrt{1-t^2}}, \qquad 0 \leqslant u \leqslant 1.$$ Plugging identity above into ##(1)## with ##u...
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