Question

if a+b=c where a=b=c find the angle between a+b and a-b

Answer 1

Answer:

It is given that  a+b=c  which generally implies that, the vectors a, b, and c  form a triangle.

Next, it is also given that  |a|+|b|=|c|  where each term in the above equation denotes the length of the sides of the triangle formed by vectors.

However, the sum of two sides of a triangle is always greater than the third side. But in the above equation, the sum of the other two sides is equal to the third side which means the vectors a, b, and c  are collinear. So the angle between a  and b  is zero.