Please answer the questions below

15. Describe the given set with a single equation or with a pair of equations. . The plane through the point (3, -1, 2) perpendicular to the r-axis . The plane through the point (3, -1, 1) parallel to the ry-plane 16. Find the cosine of the angle between v and u v = 2i + 10j - 11k, u = 2i + 2j + k . v = 5j - 3k, u = i+ j + k 17. Find the areas of the parallelograms whose vertices are A(1, 0), B(0, 1), C(-1, 0), D(0, -1) 18. find the length and direction (when defined) of u x v and v x u. u = 2i-2j-k, v=i-k 19. Find parametric equations for the line through the point P(3, -4, -1) parallel to the vector i + j + k 20. Find parametric equations for the line through P(1, 2, -1) and Q(-1, 0, 1) 21. Find equations for the plane through P(0, 2, -1) normal to n = 3i - 2j - k 22. Find equations for the plane through (1, -1, 3) parallel to the plane 3x + y + z = 7 23. Find equations for the plane through (1, 1, -1), (2, 0, 2), and (0, -2, 1) 24. find the distance from the point to the line. (0, 0, 12); x = 4t, y = -2t, z = 2t 25. find the distance from the point to the plane. (2, -3, 4), x + 2y + 2z = 13 26. Sketch the graph of the function f(x, y) = x2 + 2 27. Determine whether the following limit exist or not lim xy2 - 1 lim sin(x2 + y2) x3 + 73 lim my + 1 lim (x,y)- (1,1) y - (,y) -+ (1,-1) x2 - 12 (x,y)-+ (0,0) x2 + y2 (x,y)- (1,-1) xty 28. Find fx, fy, fax, fay, fyy . f(x,y) = x2 - xy + y2 . f(x, y) = In(x + y) . f(x, y, z) = x - Vy2 + z2 . W= T2 ty 29. w = x2 +y', x = cost + sint, y = cost - sint Find dw/dt