Which equation represents the pythagorean theorem, which can be used to find the magnitude of resultant vectors?

r = a + b

r = a x b

r2 = a2 x b2

r2 = a2 + b2

I will use capital letters to represent vectors.

To find a vector (magnitude + direction):

R  = A + B

To find only the direction of the vector:

theta = tan^-1(ycomponent/xcomponent)

To find the magnitude only ( your question)

R^2 = A^2 + B^2
R = sqrt( A^ 2 + B^2)  (last option: D)

Ineed the problem dude