Let `veca,vecb and vecc` be three vectors such that `vecane0, |veca|=|vecc|=1,|vecb|=4and |vecbxxvecc|=sqrt15`. If `vecb-2vecc=lambdaveca` then find the value of `lambda` .

Explanation

To solve the problem, we will follow these steps:

### Step 1: Understand the given information
We have three vectors \( \vec{a}, \vec{b}, \vec{c} \) with the following properties:
- \( |\vec{a}| = |\vec{c}| = 1 \)
- \( |\vec{b}| = 4 \)
- \( |\vec{b} \times \vec{c}| = \sqrt{15} \)
- \( \vec{b} - 2\vec{c} = \lambda \vec{a} \)
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