The `vec a` is twice as long as `vec b` . Let the magnitude of `vec b` = L, `|vec a| ` = 2*L.

As the angle between the vectors is 16, the magnitude of the cross product is L*2*L*sin 25 = 16

=> 2*L^2*sin 25 = 16

=> L = `sqrt(8/sin 25)`

=> `~~4.3508`

**The magnitude of b, `|vec b| ~~ 4.3508` **

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