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### absolute value for the ln function

I tried to execute this but could not figure out the absolute value sign correctly

$c = var('c')$

$c=-0.999$

$(sqrt(1-c^2)/Pi)[2.239539+(c/sqrt(1-c^2))ln|(0.9sqrt(1-c^2)-c0.435889)/(0.9sqrt(1-c^2)+c0.435889)|+(1.8*sqrt(0.19)/(0.81-c^2)]$

I need help on the correct symbol for the absolute value for the ln function.

### absolute value for the ln function

I tried to execute this but could not figure out the absolute value sign correctly

$c c = var('c')$var('c')
c=-0.999
$c=-0.999$ $(sqrt(1-c^2)/Pi)[2.239539+(c/sqrt(1-c^2))ln|(0.9sqrt(1-c^2)-c0.435889)/(0.9sqrt(1-c^2)+c0.435889)|+(1.8*sqrt(0.19)/(0.81-c^2)]$N=(sqrt(1-c^2)/Pi)*[2.239539+(c/sqrt(1-c^2))*ln|(0.9*sqrt(1-c^2)-c*0.435889)/(0.9*sqrt(1-c^2)+c*0.435889)|+(1.8*sqrt(0.19)/(0.81-c^2)];N


I need help on the correct symbol for the absolute value for the ln function.function. Also, how am I to vary the value of c. I know is should use the command for. Example for c=0.999, 0.901, -0.999, then yield the value of N.