   Derivatives of ln y and sin ^-1 (y)
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Video Lecture 12 of 18
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### Lecture Description

Make a chain of a function and its inverse: f^-1(f(x)) = x starts with x and ends with x.
Take the slope using the Chain Rule. On the right side the slope of x is 1.
Chain Rule: dx/dy dy/dx = 1
Here this says that df^-1/dy times df/dx equals 1.
So the derivative of f^-1(y) is 1/ (df/dx) but you have to write df/dx in terms of y.
The derivative of ln y is 1/ (derivative of f = e^x) = 1/e^x. This is 1/y, a neat slope. Changing letters is OK: The derivative of ln x is 1/x. Watch this video for graphs.

### Course Description

Highlights of Calculus is a series of short videos that introduces the basics of calculus—how it works and why it is important. The intended audience is high school students, college students, or anyone who might need help understanding the subject.

The series is divided into three sections:
Introduction
- Why Professor Strang created these videos
- How to use the materials

Highlights of Calculus
- Five videos reviewing the key topics and ideas of calculus
- Applications to real-life situations and problems
- Additional summary slides and practice problems

Derivatives
- Twelve videos focused on differential calculus
- More applications to real-life situations and problems
- Additional summary slides and practice problems

Acknowledgements
Special thanks to Professor J.C. Nave for his help and advice on the development and recording of this program.The video editing was funded by the Lord Foundation of Massachusetts.