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8. [-/1 Points] DETAILS LARCALC11 12.1.051. Represent the plane curve by a vector-valued function. x 2 + 12 = 4 r(t) = Need Help? Read It Watch It9. [-/1 Points] DETAILS LARCALC11 12.1.059. Sketch the space curve represented by the intersection of the surfaces. Surfaces Parameter x2 + y2+ 22 = 4, x+z=2 x = 1 + sin t -9 -2 2 O O -21 -3 -T O Represent the curve by a vector-valued function r(t) using the given parameter. r(t) = (positive y portion) r(t) = (negative y portion)10. [-/1 Points] LARCALC11 12.1.069. ASK YOUR TEACHER PRACTICE AN OTl- Find the limit (if it exists). (If an answer does not exist, enter DNE.) lim eSti + 5'"(6')j + e'gtk r > 0 6t Need Help? 11. [/1 Points] LARCALC11 12.1.071. ASK YOUR TEACHER PRACTICE ANOTl- Determine the interva|(s) on which the vector-valued function is continuous. (Enter your answer using interval notation.) 1 rt: () 2t+1 . 1. I+_ (\"1 Need Help? 5:1, 12. [-/1 Points] LARCALC11 12.1.081. ASK YOUR TEACl- The outer bottom edge of a staircase is in the shape of a helix of radius 1 meter. The staircase has a height of 4 meters and makes two complete revolutions from top to bottom. Find a vector-valued function for the staircase. Use a computer algebra system to graph your function. (There are many correct answers Use t as the parameter. Let 0 S t S 411.)