Question

The resultant of vectors OA and OB is perpendicular to OA. Find the angle AOB

Answer 1

The figure is missing, however as per the correct question -

Given:

OA = 4m

OB = 6m

To Find:

Angle AOB

Solution:

R² = A² + B² + 2ABcos θ

Tan = Bsinθ /Bcosθ  + A

θ  = 90

Bcosθ  + a = 0

Cosθ  = -A/B

Thus,  

R² = A² + B² + 2AB ( -A/B)

= 16 + 36 - 2(16)

= 36-16

= 20

R = √20

θ = Cos -4/6

θ = Cos -2/3

θ = 131.8°

Answer: The value of ∠AOB is 131.8°