1. Find the total differential dwfor w = ytan x -2xy+el= 2. For f(x, y) = x + 3xy -y, find the total differential df . Then if x changes from 3.0 to 3.05 and y changes from 4.0 to 3.96, what is df ? 3. The efficiency of a particular engine is defined by the expression: E =0.4967 / where T is the temperature and I'is the speed. The temperature is currently at 7" =20"C and the speed, I" = 35km/hr . If the temperature decreases to 7 =19.8"C and the speed increases to /" =35.5km/hr . Use differentials to approximate the change in E. 4. A triangular field has the following nominal measurements: x =150 ft y =200 ft 0=70" . The survey equipment, however, has possible error of up to half-a-foot in the distance measurements and 2" in the angular measurement. Use differentials to find the variation in r the surveyed area of this field