• Want to level up your HSC prep on those harder Maths questions?
    Register now for the BoS Trials (7th October)!

differentiating inverse trig (1 Viewer)

zinc

Member
Joined
Jun 29, 2006
Messages
58
Gender
Female
HSC
2008
how do you differentiate
y=tan-1(1/x) and y=1/(sin-1x)
thanks
 

independantz

Member
Joined
Apr 4, 2007
Messages
407
Gender
Male
HSC
2008
y=arctan(1/x)
y'=1/(1+(1/x)^2)


y=1/arcsinx=(arcsinx)^-1
y'=(-1)(arcsinx)^-2 x(1/sqrt(1-x^2)), by the chain rule.
=-1/(sqrt(1-x^2))(arcsinx)^2
 

vds700

Member
Joined
Nov 9, 2007
Messages
860
Location
Sydney
Gender
Male
HSC
2008
independantz said:
y=arctan(1/x)
y'=1/(1+(1/x)^2)


y=1/arcsinx=(arcsinx)^-1
y'=(-1)(arcsinx)^-2 x(1/sqrt(1-x^2)), by the chain rule.
=-1/(sqrt(1-x^2))(arcsinx)^2
the first one is wrong...

y = arctan(1/x) , let u = 1/x = x^-1
dy/dx = dy/du . du/dx
=1/(1 + u^2). -x^-2
= -1/{[1 + (1/x^2)] . x^2}
= -1/(x^2 + 1)
 
Last edited:

lyounamu

Reborn
Joined
Oct 28, 2007
Messages
9,987
Gender
Male
HSC
N/A
vds700 said:
the first one is wrong...

y = arctan(1/x) , let u = 1/x = x^-1
dy/dx = dy/du . du/dx
=1/(1 + u^2). -x^-2
= -1/{[1 + (1/x^2)] . x^2}
= -1/(x^2 + 1)
Yeah, I think Andrew is right based on his working out.
 

Users Who Are Viewing This Thread (Users: 0, Guests: 1)

Top