Question

use zero cross detector for triangle pulse generation.

Answer 1

The top fig shows a zero crossing detector.
And the Bottom fig shows a triangular pulse generator.
Now in the bottom fig I see two resistors R1 and R2 which are connected with the 1st opamp and the o/p of the second opamp.

I want to ask can I replace the first op amp by a zero crossing detector and what is the use of R1 and R2 in the bottom circuit..