Element A:
f(x)=tanx+cotx2−∣∣∣tanx−cotx2∣∣∣
f(x)={cotx,tanx≥cotxtanx,tanx<cotx
There are 4 points (π4,3π4,5π4,7π4) where the above function is continuous but not differentiable in (0,2π)
Element B:
f(x)=min{1,1+x3,x2−3x+3}
f(x)=⎧⎪
⎪
⎪⎨⎪
⎪
⎪⎩1+x3,x≤01,0<x≤1x2−3x+3,1<x≤21,x>2
f′(x)=⎧⎪
⎪
⎪⎨⎪
⎪
⎪⎩3x2,x≤00,0<x≤12x−3,1<x≤21,x>2
There are 2 point x=1 and x=2 where the above function is not differentiable.
Element C:
f(x)=(x+4)1/3
f′(x)=13(x+4)2/3
Not derivable at x=−4
Element D:
f(x)=⎧⎪
⎪
⎪⎨⎪
⎪
⎪⎩−π2ln(x.2π)+π2,0<x≤π2π−x,π2<x<3π2
f′(x)=⎧⎪
⎪⎨⎪
⎪⎩−π2x0<x<π2−1π2<x<3π2
f′(π−2)=f′(π+2)=−1
function differentiable at x=π2