Hello Forumites,

I want to show that f(x)= $cos^2(x)+cos^2(π/3+x)-cos(x)*cos(π/3+x)$ is a constant function. What is it's value?

Solution

Now,to prove f(x) is a constant function,f'(x)=0 but f'(x)=-sin(2x)-sin(2*(3x+π)/3)+sin((6x+π)/3).Now what would be a interval I in which f(b)= f(a)?