In order to find the extrema, we need to solve the equation
dxdf(x)=0(the derivative equals zero),
and the roots of this equation are the extrema of this function:
dxdf(x)=the first derivative(x+1)2tan2(x+11)(tan2(x+11)+1)tan(x1)−x2tan(x+11)tan2(x1)+1=0Solve this equationSolutions are not found,
function may have no extrema