Question

if vectors a and b are acting right angles to each other find the magnitude of resultant

Answer 1

The vectors are at right angles to each other. Therefore "theta" = 90°

$= \sqrt{ {a}^{2} + {b}^{2} + ab \cos( \theta) } \\ = \sqrt{ {a}^{2} + {b}^{2} + ab \cos(90) } \\ \cos(90) = 0 \\ = \sqrt{ {a}^{2} + {b}^{2} + 0 } \\ = \sqrt{ {a}^{2} + {b}^{2} }$

There is your answer..

Hope this helps..

All The Best .. !!