Problem 85. Find a vector valued function that represents the curve of intersection of two surfaces: = = 4x-ty, y=1. Problem 86. Find a vector valued function that represents the curve of intersection of two surfaces: o'ty'+ 42" =4, y20, 8+23=1. Problem 87. Two objects travel along the space curves (t', 7t - 12, (' ) , (4t - 3, t', 5t - 6) . Do they ever collide? Do their paths intersect? Problem 88. Find a parametric equation for the tangent line to the curve r(t) = (In(1 + t), t cos(2t), 2') at (0, 0, 1). Problem 89. Find a parametric equation for the tangent line to the curve r(t) = (V( + 3), In(t' + 3), t) at (2, In 4, 1). Problem 90. Find the length the curve r(t) = (2t, 12, t ( 0