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## Homework Statement

Given two 2-dimensional vectors [itex]\overline{a}[/itex] and [itex]\overline{b}[/itex] of moduli l[itex]\overline{a}[/itex]l = 3u and l[itex]\overline{b}[/itex]l = 4u, and forming an

angle of 120 degrees between them, determine the modulus of the sum vector [itex]\overline{s}[/itex] = [itex]\overline{a}[/itex] + [itex]\overline{b}[/itex]

and the angle between [itex]\overline{s}[/itex] and [itex]\overline{a}[/itex].

## Homework Equations

a.b = l[itex]\overline{a}[/itex]ll[itex]\overline{b}[/itex]lcosθ

## The Attempt at a Solution

All if have calculated is the dot product of vectors a and b, coming to (6u

^{2}). I cannot seem to figure out what I can do to find the sum of these vectors only given the moduli and angle between them. Please Help :-)