[MUSIC] Welcome back to Calculus One. 
And welcome to Week 4 of our time 
together. 
Last week, in Week 3, we introduced a 
derivative. 
We learned about the sum rule which lets 
us differentiate the sum of two 
differentiable functions. 
This week, in Week 4, we're going to 
learn more rules for differentiation. 
We're going to learn about the product 
rule, which differentiates a product of 
two differentiable functions, and a 
quotient rule, for differentiating the 
quotient of two differentiable functions. 
We'll also learn how to differentiate 
e^x. 
Nearer the end of the week, we're going 
to look at curve sketching. 
We're going to learn how to draw pictures 
of functions not just using the infernal 
computer for drawing those pictures, but 
instead by using paper and pencil and our 
human minds for drawing reasonably good 
pictures of functions. 
I also want to thank you. This course is 
a ton of work and you've been doing a 
fantastic job thus far. 
But, it's not just about us teaching you 
calculus, it's about you teaching us how 
to run a course like this. 
Your participation make possible 
improvements to the course which will 
bring calculus to thousands more people. 
And for that, I thank you.