How to simplify ArcSin formula

*To*: mathgroup at smc.vnet.net*Subject*: [mg123249] How to simplify ArcSin formula*From*: David Sagan <david.sagan at gmail.com>*Date*: Tue, 29 Nov 2011 07:04:08 -0500 (EST)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com

I am trying to discover how to simplify xxx where xxx is defined to be: xxx= t + ArcSin[aa] - ArcSin[aa Cos[t] + Sqrt[1 - aa^2] Sin[t]] with -1 < aa < 1 The answer I know is xxx = 0 but the reason I am posing the question is that I am interested in finding out, in general, how to manipulate formulas of this type. I tried: FullSimplify[xxx, -1<a<1] but that did not work. Can anyone tell me how to do this? -- Thanks, David