I think you can try to create your own authentication cookie containing a custom authentication ticket. 

Refer to this msdn article on how to create your own auth ticket and cookie

http://msdn.microsoft.com/en-us/library/ff649204.aspx

ASP.NET membership/ automatically log existing user on

  Use sketch to find exact value of $\tan (\cos^{-1}\dfrac{5}{13})$


I drew a right triangle with angle $\theta$ and sides $12,5,3.$
If $\cos \theta=\frac{5}{13},$ then $\sin \theta = \frac{12}{13}$ and $\tan \theta = \frac{12}{5}.$  

This isn't correct since tangent is greater than one. How would I solve this correctly? (Please show steps) Thanks.
