Evaluate the aspect ratio of a triangle
Jelly, 7 bytes

SH_÷@HP


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Explanation



Let’s read this chain:


The implicit argument is a list [a, b, c].
First we read S. This takes the sum: a + b + c.
Then, we read H. This halves it: (a + b + c)/2. (This is s.)
Then, we read a dyad _ (subtract), followed by another dyad. This is a hook: it lacks a right argument, so it receives the argument to this chain, [a, b, c], giving us [s-a, s-b, s-c]. (This is the fifth chain pattern in the table here.)
Then, we read the dyad-monad pair ÷@H. This is a fork: ÷@ is division with the arguments flipped, and H is halve, so our working value gets Half the argument to this chain ÷’d by it. This vectorizes; we’re left with [(a/2)/(s-a), (b/2)/(s-b), (c/2)/(s-c)]. (This is the second chain pattern in the table here.)
Finally, we take the product with P, getting us abc/(8(s-a)(s-b)(s-c)).


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