Two vectors `vecA` and `vecB` have precisely equal magnitudes. For the magnitude of `vecA + vecB` to be larger than the magnitude of `vecA- vecB` by a factor n, what must be the angle between them ?

Explanation

`|vecA + vecB| =n|vecA-vecB|`
`2A costheta/2 =n2A sintheta/2 (A=B)`
`therefore tan theta/2 =1/n, theta/2 = tan^(-1)(1/n), theta = 2tan^(-1)(1/n)`