The resultant of two vectors ` vecA and vecB ` is perpendicular to ` vecA ` . Magnitude of Resultant ` vecR ` is equal to half Magnitude of ` vecB ` . Find the angle between ` vecA and vecB `?

Explanation

Since `vecR` is perpendicular to `vecA`. figure shows the three vectors `vecA, vecB and vec`R.
angle between `vecA and vecB` is p-q
`"sin" q=(R)/(B)=(B)/(2B)=(1)/(2)`
`rArr q=30^(@) rArr` angle between A and B is `150^(@)`