Work Step by Step
See sec.1-8, Intermediate Value Theorem. If f is continuous on [a,b], N any number between f(a) and f(b), f(a) $\neq$ f(b). Then, there exists a c in [a,b] such that f(c)=N. ------------- $\pi\approx 3.14,\qquad 3 < \pi < 4$ $f(-1) < \pi < f(1)$. Apply the Intermediate Value Theorem with $a=-1,\ b=1,\ N=\pi$. The statement is true.