The problem of finding the minimum (or the maximum) of a function is a familiar application of calculus. However, if the derivative of the function in question is not known, one must resort to numerical methods.
Issue 2
The famous formula of Heron connects the sides, $a,b,c$ of a triangle with the area, $A$ of the triangle, i.e.
$$ A = \sqrt{s(s-a)(s-b)(s-c)}$$
Issue 3
A professor of mathematics at the University of Queensland recently recounted that when she telephoned Griffith University some years ago and asked for the Mathematics Department the receptionist replied, 'We do not have a Mathematics Department. Mathematics is not relevant to the Human Condition".