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## Homework Statement

find the velocity vector for the time t=2s

i have given r(t)=

(50*sin((1/2)*t)*cos ((1/4)t),

-50*sin((1/2)*t)*sin((1/4)t))

## Homework Equations

i also know that r(t)=

(50*sin(k*t)*cos (1/2k*t),

-50*sin(k*t)*sin(1/2k*t))

where k = 0,5s

^{-1}

## The Attempt at a Solution

so i tried solving it and my attempt is shown in the attachment where i got the result

v(2)=6,8;-15,7

but someone said it has to be solved with the following results

25m/s*[0,272449, -0,62826] so im quite confused now..

so i dont know what to do and HOPE VERY MUCH someone will check my result v(2)=6,8;-15,7 and tell me if its right or not and if so what i can do to get the right result