## anonymous one year ago If I am doing the derivative of cross product of two vectors - can I first take the cross product then take the derivative - or do I have to use the cross product rule for derivatives

1. anonymous

@robtobey

2. anonymous

I am pretty sure it will work both ways just one longer than the other

3. Michele_Laino

we can show that the first derivative of a cross product between two vectors, say a, and b is given by the subsequent identity: $\Large \frac{d}{{dt}}\left( {{\mathbf{a}} \times {\mathbf{b}}} \right) = \frac{{d{\mathbf{a}}}}{{dt}} \times {\mathbf{b}} + {\mathbf{a}} \times \frac{{d{\mathbf{b}}}}{{dt}}$

4. Jhannybean

Known as the Product Rule

5. Jhannybean

Both methods should work out fine, like you said, one would just take a little longer.