A function f is defined by f(x)=∫0πcostcos(x−t)dt , 0≤x≤2π , then which of the following hold(s) good?
a. f(x) is continuous but not differentiable in (0,2π)
b. Maximum value of f is π
c. There exists atleast one c∈(0,2π) if f′(c)=0
d. Minimum value of f is −2π