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## Homework Statement

Find the primitive function s(t) for v(t)=3(sin(3t) + cos(3t)) for which s(0)=0

## The Attempt at a Solution

v(t) =3(sin(3t) + cos(3t)) = 3sin3t +3cos3t

s(t) =cos3t -sin3t + C

0 = cos3(0) - sin3(0) + C

0= 1 + C

C=-1

such that my primitive function is cos3t - sin3t - 1

My teacher got another answer:

s(t) = -cos(3t) + sin(3t) + C

and s(0) = 0 = -1 + 0 + C such that C= 1 and the primitive function is sin3t -cos3t + 1

has he made a mistake? or am I confused?