Solve the equation for x where x is restricted to the given

Solve the equation for x, where x is restricted to the given interval, y = - 5 + 4cos x, for x in [0, pi] (Use integers or fractions for any numbers in the expression.)

Solution

Here for solving this equation for x, we put y=0, so equation remains

-5 +4cos x=0

or 4cos x= 5

or cos x =5/4 that is more than 1.

But as the value of cos function can not be more than 1, that means 5/4 can never be a value of any value of x.
Or answer is that

: x has no value in given interval.