# Partial derivatives 2 | Multivariable Calculus | Khan Academy | Summary and Q&A

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August 9, 2008
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Partial derivatives 2 | Multivariable Calculus | Khan Academy

## TL;DR

This video explains the concept of partial derivatives and how to calculate them, as well as how to find the slope of tangent lines on a given surface.

## Key Insights

• 🫡 Partial derivatives quantify how a function changes with respect to individual variables while keeping the others constant.
• 🫥 Tangent lines on a surface can be determined by taking partial derivatives at a specific point and represent the slope of the function in different directions.
• 🏑 Partial derivatives are essential in various fields to understand and analyze complex systems with multiple variables.
• ☠️ The concept of partial derivatives can be applied to real-world problems, providing insights into rates of change and sensitivity to different factors.
• 👻 Understanding partial derivatives allows for better visualization and interpretation of functions in multi-dimensional spaces.
• ✋ By taking multiple partial derivatives, it is possible to calculate higher-order derivatives and analyze more complex functions.
• 🖐️ Partial derivatives play a crucial role in optimizing functions and finding maximum or minimum values in optimization problems.

## Transcript

Before we move on to other functions, let's also take the partial derivative of our function here, f of xy, or the partial derivative of z with respect to y. So let's do it in magenta. So the partial derivative of z with respect to y. Well, now we're saying how much does z change with respect y if x is constant. So this x squared we treat as a cons... Read More

### Q: What is a partial derivative?

A partial derivative measures how a function changes with respect to only one variable while keeping the other variables constant. It allows us to analyze the sensitivity of the function to changes in a specific variable.

### Q: How do you calculate a partial derivative?

To find the partial derivative of a function with respect to x, you treat y as a constant and take the derivative of the function with respect to x. Similarly, to find the partial derivative with respect to y, you treat x as a constant and take the derivative with respect to y.

### Q: What is the significance of tangent lines in partial derivatives?

Tangent lines on a surface represent the slope of the function at a specific point. By taking partial derivatives, we can determine the slope of the function in the x and y directions at that point, which helps in visualizing the changes in the function.

### Q: How can partial derivatives be applied in real-world scenarios?

Partial derivatives are widely used in fields such as physics, economics, and engineering. They help in understanding the rate of change of various quantities in systems that involve multiple variables, allowing for more accurate predictions and analysis.

## Summary & Key Takeaways

• Partial derivatives allow us to measure how a function changes with respect to only one variable while keeping the others constant.

• The partial derivative of a function with respect to x is found by taking the derivative of the function with respect to x while treating y as a constant.

• The partial derivative of a function with respect to y is found by taking the derivative of the function with respect to y while treating x as a constant.

• Tangent lines on a surface can be determined by taking the partial derivatives of the function at a given point.