Adding Vectors

Hi there!  

This isn't really the right forum to ask specific math questions like yours.  A better spot would be in the comment area of the video associated with the task ( https://www.khanacademy.org/math/precalculus/vectors-precalc/vector-addition-subtraction/v/adding-and-subtracting-vectors , maybe?) -- in fact, the answer might already be there in the comments.

Just to point something out for anyone who passes by this thread, the "A+B" in the images is just referring to the fact that vector A and vector B have to be combined, and that when added appropriately (horizontal with horizontal components, vertical with vertical components) you get the "resultant" vector A+B.

You cannot simply add the value of A and the value of B to get "A+B".  You must break them down into their components, add those, draw the new triangle using the new sum horizontal and sum vertical, and then use Pythagoras' theorem.