Suppose r(t) and s(t) are vector functions with r(2)=⟨1,2,−1⟩, r′(t)=⟨3,0,4⟩, and s(t)=⟨t,t^2,t^3⟩. (a) Find the value of f′(2), when f(t)=r(t) * s(t) (b) Find the value of u′(2), when u(t)=r(t) xx s(t).

Leonidas Cook

Leonidas Cook

Open question

2022-08-20

Suppose r ( t ) and s ( t ) are vector functions with r ( 2 ) = 1 , 2 , 1 , r ( t ) = 3 , 0 , 4 , and s ( t ) = t , t 2 , t 3
(a) Find the value of f′(2), when f ( t ) = r ( t ) · s ( t )
(b) Find the value of u′(2), when u ( t ) = r ( t ) × s ( t )
To find the value of f(2) and u(2), I need r(t) which I do not know how to find. My guess is that since r ( t ) = 3 , 0 , 4 then r(t) could equal 3 x , 0 , 4 z

Answer & Explanation

Kristen Garrison

Kristen Garrison

Beginner2022-08-21Added 11 answers

You don't need r(t) for any t 2. By the product rule,
f ( t ) = r ( t ) s ( t ) + r ( t ) s ( t ) f ( 2 ) = 3 , 0 , 4 2 , 4 , 8 + 1 , 2 , 1 2 , 4 , 12 .
Similarly,
u ( 2 ) = 3 , 0 , 4 × 2 , 4 , 8 + 1 , 2 , 1 × 2 , 4 , 12 .

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