Nah I have a life mate!Good thing you made this as a thread so that all errors are documented in one place. Do you think you'll eventually go back through your old Marathon posts where you posted other errors and transfer them to here too?
Yeah dude, I've done some of that book before, the same one, Understanding Math, and albeit the fact that I'm finding it really helpful, I too have noticed a few mistakes.
Since we just want the slope of the tangent, we don't need to figure out the entire equation of the tangent. We can just sub. the x-value into the equation for dy/dx to get the slope.