Question

Find a·b

a=<5,2>,b=<4,5>

Answer 1

`\large\boxed{\vec{a}\circ\vec{b}=30}`

Explanation:

`\text{Let}\ \vec{u}=\left<a,\ b\right>\ \text{and}\ \vec{v}=\left<c,\ d\right>,\ \text{then}\\\\\vec{u}\circ\vec{v}=ac+bd\\\\==========================\\\\\vec{a}=\left<5,\ 2\right>,\ \vec{b}=\left<4,\ 5\right>\\\\\vec{a}\circ\vec{b}=(5)(4)+(2)(5)=20+10=30`