How to see the AC pulce varied by triac

Hello Dear.......

I have a project to control the intensity of bulb through triac.

I have gate pulse to fire the triac.

Circuit is like below:

Phase to triac(switch) to bulb to neutral.

When i give gate pulse to triac, triac is on and the bulb is gettig on also the i/p voltage is vary.

i want to see the i/p waveform on CRO, but it is not measured..... it's a problem....

How to see the i/p waveform on CRO?

Connect the circuit to the mains via an isolation transformer.

Please post a schematic.