Calculators TI 89 Integral seems wrong.... What am I missing?

[jdcirbo]

My TI 89 Platinum is returning ln(abs(cos(x))/abs(sin(x)-1)) for integral sec(x)dx. It's supposed to return ln(abs(tan(x)+sec(x)) or ln(abs(sin(x)+1)/abs(cos(x))). If you enter x=0, you get 'undefined' the way my TI 89 is doing it. It's supposed to return 0. Is this a computation error or something with the syntax of how TI Basic computes integrals?

 

[Baluncore]

Ln(abs(sin(x)+1)/abs(cos(x))) = Ln(abs(cos(x))/abs(sin(x)-1))

 

[jedishrfu]

And abs sin / abs cos = abs tan

 

[jdcirbo]

Ln(abs(sin(x)+1)/abs(cos(x))) = Ln(abs(cos(x))/abs(sin(x)-1))

I don't understand why I'm getting a "non-real result" from the calculation when I enter x=0. Why is that occurring? It should be the same regardless of which form it's written in.

 

[jdcirbo]

My TI 89 Platinum is returning ln(abs(cos(x))/abs(sin(x)-1)) for integral sec(x)dx. It's supposed to return ln(abs(tan(x)+sec(x)) or ln(abs(sin(x)+1)/abs(cos(x))). If you enter x=0, you get 'undefined' the way my TI 89 is doing it. It's supposed to return 0. Is this a computation error or something with the syntax of how TI Basic computes integrals?

UPDATE: Just to make me look like a liar... Now my TI 89 is returning 0 for x=0... ? It was returning "Non-real result" before.

 

[jedishrfu]

Is the battery charge good?