Question

if anyone knows then plzz send solution...thank you​

Answer 1

I think you meant

$b \: sin \theta = B \: sin \beta$

and

$b \: cos \theta = B \: cos\beta$

If you watch it closely you can easily see its nothing but a tan angle

put the value of tan \alpha=CD/OD

Answer 2

Answer:

refer to attachment.....

{ see the value of angle between the vector }