Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ π -¹ ² ³ °

You are not logged in.

- Topics: Active | Unanswered

Pages: **1**

**{7/3}****Member**- Registered: 2013-02-11
- Posts: 210

Can piecewise functions be differentiated?for example f(x)=2x for x<2,4 for x=2,x^2 for x>2,can f be differentiated?

There are 10 kinds of people in the world,people who understand binary and people who don't.

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 7,736

hi {7/3}

At points where the function is 'well-behaved', yes. eg. For your example, everywhere except x = 2.

At this point, it may still be ok. It is continuous there, so it passes that hurdle. You then need to consider whether there is a left limit for the chord gradient and a right limit, and whether they are the same.

So, whilst f(x) = 2x, the gradient function is 2, for all x.

Whilst f(x) = x^2, the gradient function is 2x, so the right limit, as x tends to 2, is 4.

So there is not a consistency between the gradient as x approaches 2 from the left, and the gradient as x approaches 2 from the right. So it is said that it is not differentiable at this point.

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Offline

**{7/3}****Member**- Registered: 2013-02-11
- Posts: 210

Thanks

There are 10 kinds of people in the world,people who understand binary and people who don't.

Offline

Pages: **1**