# HOW can I not get this?

1. Sep 29, 2004

### Alkatran

HOW can I not get this??

5. [1pt] A sailboat tacking against the wind moves as follows: 2.8 km at 27° east of north, 4.7 km at 28° west of north, and 3.9 km at 28° east of north. The entire trip takes 4 h 25 min. What is the magnitude of the displacement of the sailboat at the end of the trip ?

Translated: Add the vectors in the question.

/\x = 2.8*sin(27) + 4.7*sin(-28) + 3.9*sin(28) = .805 km
/\y = 2.8*cos(27) + 4.7*cos(-28) + 3.9*cos(28) = 9.910 km
/\d = sqr(/\x2 + /\y2) = 9.943 km = 9943m

What's wrong?

2. Sep 29, 2004

### faust9

Looks like you've got a math error. try emtering it into your calculator again. I get a little over 10 when I do it BTW.

3. Sep 29, 2004

### Staff: Mentor

Check your arithmetic. I get (slightly) different answers for $\Delta x$ and $\Delta y$.

4. Sep 29, 2004

### Alkatran

Thanks, got it. At least it wasn't a logic error.