There are a lot of exact formulas, but there is not an exact formula for certain restrictions on what can be used to build/express the formula. For example, there is an exact formula for the positive solution to $x^2 = 2,$ namely $\sqrt {2},$ but there is not an exact formula for the positive solution to $x^2 = 2$ if the formula is restricted to be a an expression involving a finite number of integers and a finite number of the operations of addition, subtraction, multiplication, and division.
– Dave L. RenfroJun 28 '21 at 10:55
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What makes you think there isn't an exact formula? Would you agree $2\pi r$ is the exact formula for the circunference of a circle? Keep in mind that $\pi$ has an infinite series representations much like the solution for the circumstance of an ellipse. Neither can be calculated with a finite number of steps.
– Aaron HendricksonJun 28 '21 at 11:38
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If we take a sample of "simple" closed curves, the majority of curves will not have an "exact" formula for their circumference.
– MasBJun 28 '21 at 11:41