# `2x - 2 - cos(x) = 0` Use the Intermediate Value Theorem and Rolle’s Theorem to prove that the equation has exactly one real solution.

*print*Print*list*Cite

Expert Answers

sciencesolve | Certified Educator

You need to evaluate the derivative of the function `f(x) = 2x - 2 - cos x` , such that:

f'(x) = 2 + sin x

You need to use Rolle's theorem, so you need to find the roots of the equation 2 + sin x = 0.

sin x = -2

Notice that there is no value of x for sin x = -2 sin sin x in [-1,1], hence, the equation sin x + 2 = 0 has no solution. Since the equation f'(x) = 0 has no solution, there is no change of sign for the function f(x), over the interval `(-oo,+oo), ` hence, the equation f(x) = 0 has no real solutions.