Question

If `vecP+vecQ=vecR" & "vecR` is perpendicular to `vecP`.
define angle between `vecP" & "vecQ" if " vec|P|=vec|R|-`
A. `(3pi)/(4)`
B. `(pi)/(4)`
C. `pi`
D. `(pi)/(2)`

Answer 1

If `vec|P|=vec|R|`
than `alpha=45^(@)`
So angle between `vecP" & "vecQ`.
`=90^(@)+45^(@)=135^(@)=(3pi)/(4)`