Ok so I know the idea why this is true but how would I prove it.

If $\displaystyle f(x) = x^2 + 10\sin{x}$ show that therre is a number c such that $\displaystyle f(c) = 1000$

I know the function is continous and that its range is to to infinity so it has to equal 1000 at some point but how do I prove it? Thanks