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[MUSIC] Welcome back to Calculus One. 
And welcome to Week 4 of our time 

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together. 
Last week, in Week 3, we introduced a 

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derivative. 
We learned about the sum rule which lets 

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us differentiate the sum of two 
differentiable functions. 

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This week, in Week 4, we're going to 
learn more rules for differentiation. 

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We're going to learn about the product 
rule, which differentiates a product of 

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two differentiable functions, and a 
quotient rule, for differentiating the 

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quotient of two differentiable functions. 
We'll also learn how to differentiate 

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e^x. 
Nearer the end of the week, we're going 

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to look at curve sketching. 
We're going to learn how to draw pictures 

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of functions not just using the infernal 
computer for drawing those pictures, but 

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instead by using paper and pencil and our 
human minds for drawing reasonably good 

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pictures of functions. 
I also want to thank you. This course is 

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a ton of work and you've been doing a 
fantastic job thus far. 

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But, it's not just about us teaching you 
calculus, it's about you teaching us how 

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to run a course like this. 
Your participation make possible 

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improvements to the course which will 
bring calculus to thousands more people. 

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And for that, I thank you.