_-substitution: definite integral of exponential function | AP Calculus AB | Khan Academy | Summary and Q&A
![YouTube video player](https://i.ytimg.com/vi/1ct7LUx23io/hqdefault.jpg)
TL;DR
The video explains how to calculate the definite integral of x^2 * 2^(x^3) from 0 to 1.
Key Insights
- 😑 Re-expressing the base 2 as e simplifies the problem in the context of finding the definite integral.
- 🥋 U-substitution is a useful technique to transform a complicated expression into a simpler form, making it easier to find the anti-derivative.
- 👻 Evaluating the anti-derivative at the upper and lower limits allows us to calculate the definite integral directly.
Transcript
Sal: Let's see if we can calculate the definite integral from zero to one of x squared times two to the x to the third power d x. Like always I encourage you to pause this video and see if you can figure this out on your own. I'm assuming you've had a go at it. There's a couple of interesting things here. The first thing, at least that my brain doe... Read More
Questions & Answers
Q: How is the base 2 re-expressed as e in the problem?
The base 2 is re-expressed as e by finding the natural logarithm of 2, which is approximately 0.693. So, 2 can be represented as e^(0.693).
Q: Why is u-substitution used in this problem?
U-substitution is used to simplify the expression and make it easier to find the anti-derivative. By defining u = x^3 * ln(2), we can rewrite the expression in terms of u and its derivative du.
Q: What is the anti-derivative of e^u?
The anti-derivative of e^u is simply e^u, as mentioned in the video. So, the integral of e^u du is equal to e^u + C, where C is the constant of integration.
Q: How is the definite integral calculated from 0 to 1?
To calculate the definite integral, you need to evaluate the anti-derivative at the upper limit (1) and subtract the evaluation at the lower limit (0). This eliminates the constant of integration and gives you the final result.
Summary & Key Takeaways
-
The video begins by discussing the need to re-express the base 2 as e in order to simplify the problem.
-
Using u-substitution, the video transforms the expression into the anti-derivative of e^u, where u = x^3 * ln(2).
-
After finding the anti-derivative, the video evaluates it at 1 and subtracts the evaluation at 0 to obtain the final result of 1/natural log(8).
Share This Summary 📚
Explore More Summaries from Khan Academy 📚
![Impact on median and mean when removing lowest value example | 6th grade | Khan Academy thumbnail](https://i.ytimg.com/vi/-2OOBEBq9-4/hqdefault.jpg)
![Writing equations in all forms | Algebra I | Khan Academy thumbnail](https://i.ytimg.com/vi/-6Fu2T_RSGM/hqdefault.jpg)
![Missing value addition and subtraction problems with negative numbers | 7th grade | Khan Academy thumbnail](https://i.ytimg.com/vi/-4bTgmmWI9k/hqdefault.jpg)
![Interview with Karina Murtagh thumbnail](https://i.ytimg.com/vi/-2K-vDHc53Q/hqdefault.jpg)
![Simple model to understand r and g relationship thumbnail](https://i.ytimg.com/vi/--VYlmbkzNY/hqdefault.jpg)
![Breakthrough Junior Challenge Winner Reveal! Homeroom with Sal - Thursday, December 3 thumbnail](https://i.ytimg.com/vi/-4BaQqX871k/hqdefault.jpg)