Question

the magnitude of vector A ,B and C are 12 ,5 ,13 units and A+B =C then angle between A and B is pi/2 pi/4

Answer 1

The angle between A &B is pi/2 i.e 90° . Because the resultant vector C is expressed by triangle law of vector addition. As the magnitude of vector, i.e their length is 12,5 &13.
so the triangle formed if right angled triangle, as it follows pythagorous theorem. Therefore the angle between A and B is right angle, i.e pi/2.