The vectors a and b are unit vectors that make an angle of 60 degrees with each other. If a-3b and ma+3b are perpendicular, determine the value of m. I'm lost and am not sure on how to begin solving this question.
$\left \langle a,b \right \rangle$ = $\left \| a \right \|$.$\left \| b \right \|$.cos(60) but a and b are unit vectors so $\left \langle a,b \right \rangle$ = cos(60). $\left \langle a-3b,ma+3b \right \rangle$ = 0 because cos(90) = 0. You should be able to conclude the rest.