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
A Place Called Here never expecting to become missing herself as she discovers the world where everything which has ever been lost goes to, a place called Here. Jack goes on a search for Sandy believing that she is the key to finding his brother but learning more about her personal life than he should. Meanwhile, Sandy's possessions keeps getting lost from Here but found in this world. Something is bound to happen but the both of them have yet to know what it is. She was named Sandy because when she was born, her hair had the colour of sand. Although, they turned