For vectors A,B and C, given that A+B=C and that C is perpendicular to A. Further, if |A|=|C|, then what is the angle between A and B (in radians)?
Given that, A+B=C and C⊥A. It is shown in the diagram below.
From the diagram, we can say
Bcosθ=C and Bsinθ=A
But, A=C [also given]
⇒Bcosθ=Bsinθ
⇒tanθ=1 or θ=45∘
∴ Angle between A and B is 90∘+45∘=135∘ or 3π4 rad