# Quick error propagation problem

1. Nov 16, 2008

### mjolnir80

1. The problem statement, all variables and given/known data
we are trying to find the x -component of a velocity vector (V*cos$$\theta$$)
our uncertainty for the velocity is +-.0003 and for the and it is .5(in degrees)
how do we propagate the error for this
v=.048 while $$\theta$$ =27 degrees

2. Relevant equations

3. The attempt at a solution
using partial derivatives :
(vSin$$\theta$$).5 (degrees)+ (cos$$\theta$$).0003=
(0.048*sin27)0.5+(cos27).0003=0.02
the problem is this is a really big uncertainti compared to the answer and i was just wondering whether i did this right?

2. Nov 16, 2008

### gabbagabbahey

The method looks fine except that you need to convert your error to radians, as the relation $$\frac{d}{d \theta} \cos \theta=- \sin \theta$$ is only true when $\theta$ is in radians.

3. Nov 16, 2008

### mjolnir80

thanks allot!!!