# Stokes' theorem proof part 4 | Multivariable Calculus | Khan Academy | Summary and Q&A

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June 23, 2012
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Stokes' theorem proof part 4 | Multivariable Calculus | Khan Academy

## TL;DR

This video explains the proof of Stokes' Theorem, focusing on the line integral over the boundary C and comparing it to the result obtained from the theorem.

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### Q: What is the main focus of this video?

The main focus of this video is the proof of Stokes' Theorem, specifically exploring the line integral over the boundary C and comparing it to the theorem's result.

### Q: How is the line integral over the path C1 calculated?

The line integral over the path C1 is calculated by taking the dot product of the vector field G and the differential element dr, which is dx/dt dt plus dy/dt dt. This allows the line integral to be expressed in terms of the parameter t.

### Q: How is the path C parameterized?

The path C is parameterized using a position vector r, where x and y are functions of t (the parameter) and z is a function of x and y.

### Q: What is the purpose of introducing the z component in the parameterization of the path C?

The z component tells us how high above the xy plane each point on the path C should be. It allows for a three-dimensional representation of the path.

## Summary & Key Takeaways

• The video begins by discussing the line integral over the boundary C in the context of Stokes' Theorem.

• A detour is taken to introduce a vector field G and discuss its line integral over a path C1 in the xy plane.

• The concept of parameterization is briefly reviewed, and the line integral is expressed using derivatives.

• The parameterization for the path C (which is above the xy plane) is introduced, incorporating a z component based on functions of x and y.

• The video concludes by setting the stage for discussing the line integral of f dot dr along the path C.