# ti-83 neg logs.

• May 1st 2012, 04:56 AM
noork85
ti-83 neg logs.
i have never used a graph calculator before in my life, first time touching it. i prefer the hand method right now for precal, but i want to be able to confirm my answers. i have a ti-83, i imagine its old, been sitting around for a while....should i upgrade?

ok the problem i need to graph is -log3x+2

a step by step guide would be appreciated, i attempted but it just said error.

thanks guys! i would spend time with tutorials but i have an exam tomorrow.
• May 1st 2012, 05:11 AM
Prove It
Re: ti-83 neg logs.
Quote:

Originally Posted by noork85
i have never used a graph calculator before in my life, first time touching it. i prefer the hand method right now for precal, but i want to be able to confirm my answers. i have a ti-83, i imagine its old, been sitting around for a while....should i upgrade?

ok the problem i need to graph is -log3x+2

a step by step guide would be appreciated, i attempted but it just said error.

thanks guys! i would spend time with tutorials but i have an exam tomorrow.

You can only graph logarithms of base 10 and base e on a TI-83. So you will need to change the base...

\displaystyle \displaystyle \begin{align*} y &= \log_3{x} \\ 3^y &= x \\ \ln{\left(3^y\right)} &= \ln{x} \\ y\ln{3} &= \ln{x} \\ y &= \frac{\ln{x}}{\ln{3}} \\ \log_3{x} &= \frac{\ln{x}}{\ln{3}} \end{align*}

So you will need to enter \displaystyle \displaystyle \begin{align*} Y_1 = -\left(\ln{x}\right) / \left( \ln{3} \right) + 2 \end{align*}
• May 1st 2012, 05:13 AM
noork85
Re: ti-83 neg logs.
oh. thanks. which calc should i get so that i can just plug in numbers directly? and not have to go through this? or is it inevitable?
• May 1st 2012, 05:13 AM
biffboy
Re: ti-83 neg logs.
Use the fact that log to base 3 of x= logx/log3
• May 1st 2012, 05:15 AM
noork85
Re: ti-83 neg logs.
then what do i do for the x+2?
• May 1st 2012, 05:15 AM
Prove It
Re: ti-83 neg logs.
Quote:

Originally Posted by noork85
oh. thanks. which calc should i get so that i can just plug in numbers directly? and not have to go through this? or is it inevitable?

I know that the TI N-spire and any newer version allows you to input any logarithm.
• May 1st 2012, 05:17 AM
noork85
Re: ti-83 neg logs.
thanks buddy, ill def look into that. hopefully before tomorrow. ive alot to cram as it is i dont want to remember what to do on the calc as well..yet atleast.
• May 1st 2012, 12:34 PM
noork85
Re: ti-83 neg logs.
omg, thanks so much for rec. its like a computer! got th cx version, and im in love with it.