- #1
macjack
- 11
- 0
Can anyone tell me whether sin|x| and cos|x| is differentiable at x=0 ?
As far as i know, cos(x) and sin(x) is differentiable at all x.
If i try to solve this,
lim h->0 (f(x+h) - f(x))/h
when x=0, and substitute cos|x| for f(x).
lim h->0 (cos|h| - cos|0|)/(h) = 1,
so cos|x| is differentiable at x=0 right ?
And for sin|x| ...if i continue doing the same as my previous try,
lim h->0 (sin|h| - sin|0|)/(h) = limh->0 sin|h|/h = 1 .
So both are differenatiable at x=0 as per my explanation,
but the answer given is in another way.
Can you please let me whether it is correct or not ?
Thanks
Mac
As far as i know, cos(x) and sin(x) is differentiable at all x.
If i try to solve this,
lim h->0 (f(x+h) - f(x))/h
when x=0, and substitute cos|x| for f(x).
lim h->0 (cos|h| - cos|0|)/(h) = 1,
so cos|x| is differentiable at x=0 right ?
And for sin|x| ...if i continue doing the same as my previous try,
lim h->0 (sin|h| - sin|0|)/(h) = limh->0 sin|h|/h = 1 .
So both are differenatiable at x=0 as per my explanation,
but the answer given is in another way.
Can you please let me whether it is correct or not ?
Thanks
Mac