1. The problem statement, all variables and given/known data Our question is \int (from 0 to 4) dt/ ((4t^2) + 9) (For a better representation, because I fail at LaTeX: http://www.wolframalpha.com/input/?...&f5=4&f=DefiniteIntegralCalculator.rangeend_4 ) 2. Relevant equations So we have the rule: \int du/(a^2 + u^2) = (1/a) arctan (u/a) + C 3. The attempt at a solution So, using a = 3, and u = 2t (because the rule says that at the bottom, there is a^2 + u^2, so we take the square root of 9, and 4t^2) I get 1/3 arctan( 2t/3) from 4 to 0 1/3 arctan( 8/3) - 1/3 arctan (0) =.404.. However, Wolfram Alpha, and my graphing calculator seem to both give me .202, and wolfram alpha says the coefficient for the final solution is 1/6 arctan..., whereas I got 1/3 arctan..., and I cannot see how it becomes 1/6.. Thanks for reading!