# Newton's Method

• Aug 16th 2010, 01:10 AM
Sunyata
Newton's Method
Hi

1.a) I know if the 1st approx is taken at x2, the tangent will be parallel to the x axis. But what about x1. Why cant i use it?

2. b) Do I just say f"(0.6) and f"(0.8) are both negative and thus there must a stationary point in between?

c) How exactly do you use Newton's method to find a stationary point?

3. a) Could someone please give me hints to do this?

Thank you!!!
• Aug 16th 2010, 01:37 AM
CaptainBlack
Quote:

Originally Posted by Sunyata
Hi

1.a) I know if the 1st approx is taken at x2, the tangent will be parallel to the x axis. But what about x1. Why cant i use it

Because it will converge to the other root.

CB
• Aug 16th 2010, 01:42 AM
CaptainBlack
Quote:

Originally Posted by Sunyata
2. b) Do I just say f"(0.6) and f"(0.8) are both negative and thus there must a stationary point in between?

No, it is because f'(x) has different signs at 0.6 and 0.8.

CB
• Aug 16th 2010, 01:44 AM
CaptainBlack
Quote:

Originally Posted by Sunyata
c) How exactly do you use Newton's method to find a stationary point?

You differentiate and then use Newtons method to find a root of f'(x)=0

CB
• Aug 16th 2010, 01:47 AM
CaptainBlack
Quote:

Originally Posted by Sunyata
3. a) Could someone please give me hints to do this?

See here

CB