The Position Vector of a Particle Is R(t) $t = \frac { \pi } { 4 }$

question 50

Multiple Choice

The position vector of a particle is r(t) . Find the requested vector.
-The acceleration at $t = \frac { \pi } { 4 }$ for $r ( t ) = ( 2 \sin 2 t ) \mathbf { i } - ( 2 \cos 2 t ) \mathbf { j } + ( 5 \csc 2 t ) \mathbf { k }$

• A) \(a \left( \frac { \pi } { 4 } \right) = 8 i + 20 k\)
• B) \(a \left( \frac { \pi } { 4 } \right) = - 8 i + 20 k\)
• C) \(\left( \frac { \pi } { 4 } \right) = - 8 \mathbf { i } - 20 \mathbf { k }\)
• D) \(a \left( \frac { \pi } { 4 } \right) = 8 \mathbf { j } + 20 \mathbf { k }\)

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