For the following exercises, determine the slope of the tangent line, then find the equation of the tangent line at the given value of the parameter. 66. r = 3 sint, y = 3 cost, 1= 4 67. r = cost, y = 8 sin 1, 1 = 5 68. r = 21, y=p, t= -1 69. x=1+1, y=:-1, r= 1 70. x=vi, y = 21, 1 = 4