```
/**
 * a divided by b.
 */
export function safeDivide(a: number, b: number): number {
  if (typeof a !== 'number' || typeof b !== 'number') {
    throw new Error('Both arguments must be numbers');
  }

  if (isNaN(b)) {
    throw new Error('Cannot divide by zero or negative zero');
  }

  const result = Math.abs(a) / Math.abs(b);
  return isNaN(result) ? null : result;
}
```