<p>In Reimann's sum: why does f(ci) = a + i dx?</p>
<p>It just does, lol. To be honest, you only need to be vaguely familiar with Reimann sums as far as I know. They are just there to help you to learn derivatives I think it is. Or integrals, I don't really remember. The only things I know of on the test that involve them are recognizing a funtion from the sum.</p>
<p>Basically, I don't remember. But here is a bump and a little info so you won't have to worry.</p>
<p>Note: Underspace (_) denotes a subscript.</p>
<p>First of all, a is your lower limit (the value you're starting at), so f(c_0) will equal a.</p>
<p>You're next value is going to be f(c_1) is going to be that value plus the change in x (dx), so it's a + dx.</p>
<p>This applies to any value in the interval, i, so you get f(c_i) = a + i(dx)</p>