The resultant of two vectors `vecA "and"vecB `is perpendicular to `vecA`. Magnitude of Resultant `vecR` is equal to half magnitude of `vecB` . Find the angle between `vecA" and "vecB`?

Explanation

To solve the problem step by step, we will follow the reasoning laid out in the video transcript.

### Step 1: Understand the Problem
We have two vectors, \(\vec{A}\) and \(\vec{B}\), and we know that the resultant vector \(\vec{R}\) is perpendicular to \(\vec{A}\). The magnitude of \(\vec{R}\) is equal to half the magnitude of \(\vec{B}\). We need to find the angle \(\theta\) between \(\vec{A}\) and \(\vec{B}\).

### Step 2: Set Up the Equation for the Resultant
The magnitude of the resultant vector \(\vec{R}\) can be expressed using the formula:
\[
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