Filter löschen
Filter löschen

Different result by hand-differentiaion vs MATLAB diff() function.

2 Ansichten (letzte 30 Tage)
I differentiated the equation, ( K=(y^2 + 2*y + 2)/(y + 1)^2 ), by hand-differentiation and got result, ( -2/(y+1) ) while the result with MATLAB function, ( diff(K, y) ) was, (2*y + 2)/(y + 1)^2 - (2*(y^2 + 2*y + 2))/(y + 1)^3
I don't know why was it and what was the wrong I did.
Please help. Thank you.

Akzeptierte Antwort

Roger Stafford
Roger Stafford am 5 Mär. 2018
Bearbeitet: Roger Stafford am 5 Mär. 2018
Your "hand-differentiation" is not correct! The 'diff' answer is correct but can be simplified to an equivalent -2/(y+1)^3. (Perhaps the latter is what you meant to write?)
  5 Kommentare
Stephen23
Stephen23 am 5 Mär. 2018
@yf: considering that Roger Stafford helped you to resolve this issue then you should accept this answer: this is the easiest way for you to show your appreciation to the volunteers who help you on this forum.
Stephen23
Stephen23 am 5 Mär. 2018
yf's "Answer" moved here:
Hi Mr. Roger Stafford,
I found the problem now. the denominator in the solution manual is actually,
(y^2 + 2*y + 1)^2 = ( (y + 1)^2 )^2
hence is,
(2*y + 2)/(y + 1)^2 - (2*(y^2 + 2*y + 2))/(y + 1)^3 = -2*(y + 1)/(y+1)^4 = -2/(y+1)^3
I made mistake on this point.
Thank you so much for you answer and help.

Melden Sie sich an, um zu kommentieren.

Weitere Antworten (0)

Kategorien

Mehr zu Graphics Objects finden Sie in Help Center und File Exchange

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by