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

question 80

Multiple Choice

The position vector of a particle is r(t) . Find the requested vector.
-The velocity at $t = \frac { \pi } { 4 }$ for $\mathbf { r } ( \mathrm { t } ) = 4 \sec ^ { 2 } ( \mathrm { t } ) \mathbf { i } - 5 \tan ( \mathrm { t } ) \mathbf { j } + 10 \mathrm { t } ^ { 2 } \mathbf { k }$

• A) \(\mathbf { v } \left( \frac { \pi } { 4 } \right) = - 10 \mathbf { j } - 5 \pi \mathbf { k }\)
• B) \(\mathbf { v } \left( \frac { \pi } { 4 } \right) = - 10 \mathbf { j } + 5 \pi \mathbf { k }\)
• C) \(\mathbf { v } \left( \frac { \pi } { 4 } \right) = 16 \mathbf { i } - 10 \mathbf { j } + 5 \pi \mathbf { k }\)
• D) \(\mathbf { v } \left( \frac { \pi } { 4 } \right) = 16 \mathbf { i } + 10 \mathbf { j } - 5 \pi \mathbf { k }\)

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