Art of Electronics Question 1.14

[DrPapper]

Homework Statement

There is a circuit diagram which I can't post atm and don't think it's relevant to my question.

Also: R₁
=R₂=10k and C=.1μF

And: Find V(t)

Homework Equations

We're given the equation V(t)=1/RC ∫^t_-∞ V_i(t)e^-(t-τ)/RCdτ

My problem is I don't recall what tau is here "τ" and I'm not sure what I should be using for the V_i(τ).
I've been trying to find it in my notes and physics textbooks but I can't seem to find it. LOL I must be stuck on stupid because I know I've seen these and am familiar with them. If anyone has this book and has solved this problem please help me out. :D

The Attempt at a Solution

Found V(t) by Thevenin Analysis to be .5V_i also used Thevanin to find R_eq=20K to replace the 1/R in the integral. Not sure what else to do.

 

[BvU]

$\tau$ is an integration variable, with the dimension of time. "How long ago" is what it stands for: V(t) depends on what happened before.

No more free advice until you follow the guidelines: your complete and concise problem statement, all the given and unknown variables; the equations you intend to use and not the results of your attempt at solution, but your attempt.