80 0:57 6:56 www.wamap.org i sin(a) = cla + C323 + c525 +... with coefficients O N . C1 - . C3 = , C5 120 V Part 3 of 4 . 23 So isin(x) =ix -i7 + 7 3! 5! +... Next, add the series for cos(a) and isin (a) together to get a power series: cos(a) + isin(a) = co+ cla + C2ac2 + C3203 + CAact + with coefficients Co A N. C1 C2 - 1 O N . , C3 , C4 = 24 Part 4 of 4 Noticing that the coefficients are the same, we have proved that ell = cos(x) + isin(x) To finish, plug in ac = 7 to get a number: e 35 A