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## Homework Statement

integral from (0, 1) of:

(4r*dr)/sqrt(1 - r^4)

## Homework Equations

## The Attempt at a Solution

i know the equation is undefined at r = 1 so:

lim t --> 1 of the integral (0, t) of (4r*dr)/sqrt(1 - r^4)

by trig subsitution:

sin(x) = sqrt(1-r^4)

cos(x) = r^2

deriving implicitly gives:

-sin(x) = 2rdr

-2sin(x) = 4rdr

so i end up with:

integral (0, t) of (-2sin(x))/(sin(x))

which gives me the answer as -2

maybe my calculator is wrong? or more likely im making some stupid mistake/overlooking something.