Answer:
The derivative is [tex]\frac{ d (r(t) \cdot a(t))}{dt} = 82[/tex]
Step-by-step explanation:
From the question we are told that
[tex]r(t) = (t^2 ,1 - t , 4t)[/tex]
[tex]a(2) = (2, 5, -3)[/tex] and [tex]a'(2) = (4,-3 , 9)[/tex]
At t = 2
[tex]r(t) = (2^2 ,1 - 2 , 4(2))[/tex]
[tex]r(t) = (4 ,-1 , 8 )[/tex]
Now the derivative of r(t) is
[tex]r'(t) = (2t, -1 ,4)[/tex]
At t = 2
[tex]r'(t) = (2(2), -1 ,4)[/tex]
[tex]r'(t) = (4, -1 ,4)[/tex]
Now the derivative of [tex]r(t) \cdot a(t)[/tex] At t = 2 is
[tex]= r'(2) a(2) + a'(2)r(2)[/tex]
[tex]= (4,-1,4)(2,5,-3) + (4,-3,9)(4,-1,8)[/tex]
[tex]= (8 - 5 -12) + (16+3+72)[/tex]
[tex]= -9 + 91[/tex]
[tex]\frac{ d (r(t) \cdot a(t))}{dt} = 82[/tex]
