If the angle between two vectors is slowly increased from 0 then what changes in magnitude will be found in the resultant ?

Explanation

Let `veca and vecb` be the two vectors whose resultant is `vecR*veca` is direction along the positive x-axis and is constant, while `vecv` moves from the positive x-axis in the anticlockwise direction.
Let at any moment , the angle between `veca and vecb be theta`
`thata R=(a^2+b^2+2abcos theta)^(1//2)`
From this equation we get,
When , `theta =0 R=a+b`
When `theta =90^@, R=(a^2+b^2)^(1//2)`
when , `theta=180^@, R=|a-b|`
when ,`theta=270^@,R=(a^2+b^2)^(1//2)`
when, `theta=360^@, R=a+b`
So, when the angle increases from `0^@` to `180^@` gradually, the magnitude of R decreases from (a+b) to |a-b|. Again, when `theta` increases from `180^@` to `360^@`, the magnitude of R increases from |a-b| to (a+b).