Determine whether rolle's theorem can be applied on a closed interval [a,b]

Question

Determine whether rolle's theorem can be applied on a closed interval [a,b]

f(x)=cos x *[-π/2,π/2]

Answer 1

You guys left out differentiable on the open interval.

Answer 2

Rolle's Theorem can be applied because f(x) = cosx is continuous on

[-π/2, π/2], is differentiable on the open interval,

and f(-π/2) = f(π/2).   

Answer 3

Yes it can because the function is continuous in the interval of all real numbers.