Science:Math Exam Resources/Courses/MATH100/December 2018/Question 11 (a)/Hint 1

Start by letting $h(x)=f(x)-\frac{x+1}{2}=g(x)+\sin (x)-\frac{x+1}{2}$. Find two numbers $c_1$ and $c_2$ such that $h(c_1)>0$ and $h(c_2)<0$. Which theorem can we use now?