2. Re: vectors

Do you know how to add vectors? Break them into x- and y-components and add the components, then convert back to magnitude and direction. So - what are the x- and y- components of vectors a, b, and c? What do get for the sum of all three vectors? Finally - what is the magnitude of ths sum of all three vectors?

3. Re: vectors

That's probably the simplest thing to do. But you could also use the "cosine law".
It should be clear that $\vec{a}+ \vec{c}$ has length 10- 2= 8 and is in the direction of c.

Now, adding $\vec{b}$ to that, we have a triangle with sides of length 8 and 3 and angle 180- 120= 60 between them. The length, x, of the third side of that triangle satisifies $x^2= 3^2+ 8^2- 2(3)(8)cos(60)= 9+ 64- 48(1/2)= 49$ so x= 7. The angle, A, that side makes with $\vec{a}$ is given by the sin law: $\frac{sin(A)}{3}= \frac{sin(60)}{7}$.

4. Re: vectors

10 - 2 - 3cos(60) = 8 - 3cos(60)

= 8 - 3/2

= 13/2

The vertical components are

0 + 0 + 3sin(60) = 3sin(60

= (3/2) sqrt(2)