I have make the application of GPS which give me the Latitude and Longitude of current location, but the problem is that in some particular areas GPS doesn't provide the location. Can any one suggest me the tutorials of triangulation technique based on cell signals or wifi signals.
If an Android smartphone is unable to get a GPS fix, it can still likely determine its position using either cell tower location or WiFi positioning. Neither are as accurate, but they don't require a clear view of the sky. Here are some details on how to access and compare all three of these positioning methods: http://developer.android.com/guide/topics/location/obtaining-user-location.html#BestPerformance
I'm not sure what it is that you're hoping to triangulate based on. WiFi signals? Here's an SO question about triangulating based on cell signals.
Technically speaking, GPS uses trilateration, because it's based on distance measures rather than angular measures.