I am almost done with this exercise, but I don't get a sqrt(5) in the denominator in my final answer, thus the correct answer is: 5/sqrt(5). How come I don't get a correct answer? Is the formula used incorrect?
Last edited by kaemper; Mar 28th 2014 at 07:27 AM.
When you calculate a directional derivative, you need to do the inner product with a unit vector. The unit vector in the direction is . So when you take the dot product, you should get . I assume your answer 5/sqrt(5) is a typo.