The resultant of two vectors `vecA` and `vecb` is perpendicular to the vector `vecA` and its magnitude is equal to half the magnitude of vector `vecB`. The angle between `vecA` and `vecB` is

Explanation

To solve the problem, we need to find the angle between the two vectors \( \vec{A} \) and \( \vec{B} \) given the conditions about their resultant vector. Let's break it down step by step.

### Step 1: Understanding the Problem
We know that the resultant of two vectors \( \vec{A} \) and \( \vec{B} \) is perpendicular to \( \vec{A} \). This means that the angle between the resultant vector \( \vec{R} \) and vector \( \vec{A} \) is \( 90^\circ \).

### Step 2: Magnitude of the Resultant Vector
According to the problem, the magnitude of the resultant vector \( \vec{R} \) is equal to half the magnitude of vector \( \vec{B} \). Mathematically, we can express this as:
\[
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