Rahul was trying to solve some mathematics problems related to trigonometry. He tried many times but failed. His teacher helped him, which led him to follow the right approach and he succeeded in solving these problems. This is an example of

Succeeding after the teacher's guidance shows the zone of proximal development.

The zone is the gap between what a learner can do alone and with help.

Equilibrium is the balance between assimilation and accommodation.

Assimilation fits new information into existing schemas.

Schemas are mental frameworks for organising knowledge.

Vygotsky introduced the zone of proximal development.