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
Straight from the Heart (Patrice Rushen album) "Straight from the Heart" a "C+" and said that he prefers side one's "dancy vamp" over the songwriting on side two by Rushen, whom he called a fashionable "ingenue". In a retrospective review, AllMusic's Andy Kellman gave it four out of five stars and called it "an early-'80s jazz-pop-R&B synthesis as durable and pleasing as any other". In 2018, Pitchfork ranked Straight From the Heart #194 on its list of the 200 Greatest Albums of the 1980s. Straight from the Heart (Patrice Rushen album) Straight from the Heart is the seventh studio album by American recording artist Patrice Rushen, released