HW09-solutions - cadena(jc59484 HW09 ben-zvi(55400 This print-out should have 23 questions Multiple-choice questions may continue on the next column or

# HW09-solutions - cadena(jc59484 HW09 ben-zvi(55400 This...

This preview shows page 1 - 3 out of 12 pages. cadena (jc59484) – HW09 – ben-zvi – (55400) 2 The area and circumference of a circle of radius r are given by A = πr 2 . C = 2 πr respectively. Thus dA dt = 2 πr dr dt = C dr dt . When dr/dt = 5 ft/sec, therefore, dA dt = 5 C sq. ft./sec . 003 10.0points Determine the value of dy/dt at x = 2 when y = x 2 - 5 x and dx/dt = 3. 1. dy dt vextendsingle vextendsingle vextendsingle x =2 = 5 2. dy dt vextendsingle vextendsingle vextendsingle x =2 = - 1 3. dy dt vextendsingle vextendsingle vextendsingle x =2 = 1 4. dy dt vextendsingle vextendsingle vextendsingle x =2 = - 3 correct 5. dy dt vextendsingle vextendsingle vextendsingle x =2 = 3 Explanation: Differentiating implicitly with respect to t we see that dy dt = (2 x - 5) dx dt = 3 (2 x - 5) . At x = 2, therefore, dy dt = 3( - 1) = - 3 . 004(part1of2)10.0points A point is moving on the graph of 3 x 3 + 2 y 3 = xy . When the point is at P = parenleftBig 1 5 , 1 5 parenrightBig , its x -coordinate is decreasing at a speed of 4 units per second. What is the speed of the y -coordinate at that time? 1. speed y -coord = 15 units/sec 2. speed y -coord = 16 units/sec correct 3. speed y -coord = - 17 units/sec 4. speed y -coord = 17 units/sec 5. speed y -coord = - 16 units/sec Explanation: Differentiating 3 x 3 + 2 y 3 = xy implicitly with respect to t we see that 9 x 2 dx dt + 6 y 2 dy dt = y dx dt + x dy dt .  #### You've reached the end of your free preview.

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