An object moving along a curve in the $x y$-plane has position $( x ( t ) , y ( t ) )$ at time $t \geq 0$ with $\frac { d x } { d t } = 3 + \cos \left( t ^ { 2 } \right)$. The derivative $\frac { d y } { d t }$ is not explicitly given. At time $t = 2$, the object is at position $( 1,8 )$.
(a) Find the $x$-coordinate of the position of the object at time $t = 4$.
(b) At time $t = 2$, the value of $\frac { d y } { d t }$ is - 7 . Write an equation for the line tangent to the curve at the point $( x ( 2 ) , y ( 2 ) )$.
(c) Find the speed of the object at time $t = 2$.
(d) For $t \geq 3$, the line tangent to the curve at $( x ( t ) , y ( t ) )$ has a slope of $2 t + 1$. Find the acceleration vector of the object at time $t = 4$.