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# Mind Your Ps and Qs

##### Age 16 to 18 Short Challenge Level:

Here are 16 propositions involving a real number $x$:

 $x\int^x_0 ydy < 0$ $x> 1$ $0< x< 1$ $x^2+4x+4 =0$ $x=0$ $\cos(x/2)> \sin(x/2)$ $x> 2$ $x=1$ $2\int^{x^2}_0ydy> x^2$ $x< 0$ $x^2+x-2=0$ $x=-2$ $x^3> 1$ $|x|> 1$ $x> 4$ $\int^x_0 \cos y dy =0$

[Note: the trig functions are measured in radians]

By choosing $p$ and $q$ from this list, how many correct mathematical statements of the form $p\Rightarrow q$ or $p\Leftrightarrow q$ can you make?

It is possible to rearrange the statements into four statements $p\Rightarrow q$ and four statements $p\Leftrightarrow q$. Can you work out how to do this?

NOTES AND BACKGROUND

Logical thinking is at the heart of higher mathematics: In order to construct clear, correct arguments in ever more complicated situations mathematicians rely on clarity of language and logic. Logic is also at the heart of computer programming and circuitry.