Error making app compatible for iOS6 and iOS7

Question

I built an app on XCode 5 for iOS7 and have just downloaded the iOS6 SDK so I can make the app compatible for iOS6, however when trying to build the project I am getting this error

Undefined symbols for architecture armv7:
  "___sincos_stret",

What should I do to solve this because I really need my app working with iOS6

Here are my current settings:

Answer 1

__sincos_stret is new to iOS7. Make sure your deployment target is set to iOS6. See semi-related question here: ___sincos_stret undefined symbol when linking

Update : You need to set the Base SDK to iOS 7. You generally want to set Base SDK to the latest version you intend support, and Deployment Target to the earliest version. See related question: Base versus Active versus Deployment target

Answer 2

set the Base SDK to ios7 and set the deployment target to ios6

that way you get the headers for 7 but the app is compiled to be run on ios6