God of War 2. not able to open the door after killing prometheus

This has bogged me for 2 full months. After killing prometheus in the fire, I climbed the series of levers and pulley, collecting orbs,feathers and what not on the way to the door. But I was not able to open the door, however hard I tried. The reason being I was not able to activate the 'Rage of titan'. to do that I was suppose to press R3. I was wonder where is this R3 on my joystick. And then one day, I was able to press R3.

Let me show you where R3 was:

this key kept me bothered for months together and the finally one day, by fluke I was able to move further. Have fun. I am still very much into God of war. Every time I am stuck, I will write the resolution here.