Area of a circle trigonometry, uses the coarea formula. Define a function formula_10 by formula_11. Note ρ is a Lipschitz function whose gradient is a unit vector formula_12 (almost everywhere). Let "D" be the disc formula_13 in formula_14. We will show that formula_15, where formula_16 is the two-dimensional Lebesgue measure in formula_14. We shall assume that the one-dimensional Hausdorff measure of the circle formula_18 is formula_19, the circumference of the circle of radius "r". (This can be taken as the definition of circumference.) Then, by the coarea formula, Similar to the onion proof outlined above, we could exploit calculus in a different way in
There Goes a... There Goes Santa Claus (1995) Dave and Becky pretend to be Santa Claus and do the duties that he does. Also, this episode is a flashback episode when Dave and Becky remember what they did in the past. 15. There Goes the Mail (or There Goes a Mail Truck) (1996) Letter Carriers Dave & Becky learn about where the mail goes and how it is transported. 16. There Goes a Rescue Vehicle (1996) Dave and Becky learn about different types of rescue work and the vehicles they use. 17. There Goes a Garbage Truck (1997) Dave and Becky learn about