# Math Help - resultant between two vectors

1. ## resultant between two vectors

given vectors $\vec{a}$ and $\vec{b}$ such that the angle between the vectors is $60^o$, $|\vec{a}|=3$ and $|\vec{b}|=2$ determine $|\vec{a}+\vec{b}|$

2. Originally Posted by william
given vectors $\vec{a}$ and $\vec{b}$ such that the angle between the vectors is $60^o$, $|\vec{a}|=3$ and $|\vec{b}|=2$ determine $|\vec{a}+\vec{b}|$

Writing simply $a$ instead of $\vec{a}$ , and assuming these are real vectors, we get

$|a+b|^2=(a+b)\cdot(a+b)=a\cdot a+2a\cdot b+b\cdot b=9+4+2|a||b|\cos 60=13+6=19$

Tonio