Find all points on the graph of the function f(x) = 2 cos(x) + (cos(x))^2 at which the tangent line is horizontal. Consider the domain x = [0,2π).
to find
( , ) (smaller x value)
( pi , -1 ) (larger x value)
I found the larger solution, but not the smaller one. I know cosx = -1
I think it should be pi. The webassign says it's wrong,
and also I guessed -pi/2 and pi/2 as x . neither is right. Please help, Thanks!