View Full Version : A little antiderivative problem


Icebird
03-08-03, 03:57 PM
Question:

What's the Primitive function of:

f'(x) = -1/((1-x^2)^0.5)

... If f(x) = -arcsin(x), then f'(x) = -1/sqrt(1 - x^2)

... f(x) = -arcsin(x) + c for any constant c.

Anyone here a bit smarter than me?

SoLiDUS
03-09-03, 06:11 AM
I'm not going to attempt answering the problem (in part because
I haven't seen this yet) but I just want to point something out, in
case you've missed it:

(1-x^2)^0.5 is the same as sqrt(1 - x^2)

Hope that helps ? ;)

If not, don't mind me... :p

Persol
03-09-03, 10:45 AM
Do you have a "Schaum's Outline"? It'll probably be in there. If nobody comes up with it by tonight I'll dig mine out and find it.

BloodSuckingGerbile
03-09-03, 01:03 PM
Didn't you.... answer your own question?:bugeye:

Icebird
03-14-03, 08:30 PM
Man, that's the question.. was I right or did I just sign my own death..?

HallsofIvy
03-16-03, 01:05 PM
YES. What everyone is saying is:

Since (1-x^2)^(1/2) is the same as [sqrt](1-x^2),

The anti-derivative of both is - arcsin(x)+ C.

James R
03-16-03, 07:07 PM
The antiderivative of 1/sqrt(1-x<sup>2</sup>) is arcsin x.

Isn't the antiderivative of -1/sqrt(1-x<sup>2</sup>) equal to arccos x?

BloodSuckingGerbile
03-17-03, 04:27 AM
Yeah... it is... :o

Icebird
03-17-03, 05:40 AM
Thanks:) Then I might be around a bit longer..

RMC
03-17-03, 10:10 AM
Originally posted by Icebird
Question:

What's the Primitive function of:

f'(x) = -1/((1-x^2)^0.5)

... If f(x) = -arcsin(x), then f'(x) = -1/sqrt(1 - x^2)

... f(x) = -arcsin(x) + c for any constant c.

Anyone here a bit smarter than me?



Do you know how to actually evaluate the integral?
See attached.

BloodSuckingGerbile
03-17-03, 10:49 AM
wait...
Ii I sum up all the above posts...

arccos(x)=-arcsin(x)&nbsp;&nbsp;&nbsp;&nbsp;?

...how come?

lethe
03-17-03, 06:55 PM
Originally posted by BloodSuckingGerbile
wait...
Ii I sum up all the above posts...

arccos(x)=-arcsin(x)&nbsp;&nbsp;&nbsp;&nbsp;?

...how come?

you re forgetting the constant of integration. arccos x = pi/2 - arcsin x

BloodSuckingGerbile
03-18-03, 04:03 AM
Oh, right. Thanks. Got it.